Yeah I hear the entire World Tour professional peloton are changing over to flat pedals after reading your post.
Factitious tho your comment is, the reality is, that noone on this forum is in the world tour peloton. We have a couple of world champions in specific disciplines, including two 24 hour TT world champions, who have accounts on this forum, as well as other truly impressive athletes. The reality is we're not world tour pro's. We're not even close to that level. Most of us don't compete, we're just out riding bikes cos we like to ride bikes. To compare us with world tour pro's is a bit like comparing our driving to that of Lewis Hamilton. Yet I don't see you all going out to buy Nomex suits and HANS units so you can drive to the pub on a Sunday. Oh, and of those amazing athletes, I mention, one of them was beaten in an ultra race by a rider using walking trainers on flat pedals.
Yeah I agree with this. The only exception being fixed gesr where I use SPDs because a missed clip-in with Look/Spd-sl style can quickly turn into a ball-ache. Plus SPDs are good if you need the emergency fixed riders 2nd gear
Fixed is one area where I think pedal retention is necessary. Esp those morons who don't think they need to obey the law and have at least one working brake...
I see it, especially for noobs, as being more about keeping foot position rather than retention. When you're clipped in, it removes that tendency for the pedal axle to end up centred on the arch of the foot rather than under the ball. Toe clips do do the same, but if anything are harder to use than SPDs, especially in the mtb flavour.
Best of both worlds here - I use the Shimano pedals that are cleats one side and flats the other 
That's a double edged sword. If you aren't set up perfectly, that keeping the foot in the same position for the whole ride can lead to injury, which can set you back no end. On RatN in 2018 my Achilles blew up big time (it swelled to double normal size), I eventually found one position on the pedal that was least painful, and just didn't take the foot off the pedal for the next 30+km. With cleats, I wouldn't have much opportunity to do that.
There's some interesting research out there about mid foot cleat position. I'm still not entirely convinced about it, but it's certainly interesting to read.
Had to permit myself a chuckle this morning, fixed honking up a short rise, feeling the top of my feet hitting the uppers of my shoes and remembering how it had been noobsplained to me that this sensation was, of course, mythical. Then later dtopping heels to stretch calfs whilst spinning, and contemplating what would happen were I to use flats.
Fixed, so not relevant to the use case of the OP. As mentioned above, fixed gear is a use case for pedal retention. As the OP wrote, this is not a fixee rider...
Pulled my foot out setting off from some lights this morning (not sure how when pulling up doesn't exist). I had to giggle.
I should have been more specific in my reply when I said that pulling up is a myth. I am not saying that some riders who have trained to do so, do not pull up. I am suggesting that the need to pull up on the pedal is not actually a necessity in order to ride a bike. For your average rider out to enjoy riding their bike, there is, IMHO, no need for pedal retention, and no benefit to be had from training yourself to pull up
GCN have done a not exactly scientific look at this, it's hardly scientific, but it does suggest there's not much difference between the two.
https://www.velonews.com/training/video-gcn-investigates-real-difference-clipless-flat-pedals/This article from cycling weekly is also interesting. It's an interesting point that the power of your stroke is in pushing down, not in pulling up, and pulling up can reduce the power you can push down...
https://www.cyclingweekly.com/fitness/training/how-to-pedal-efficiently-173185https://gearandgrit.com/the-cycling-myth-that-wont-die-pedaling-circles/
No. What is a myth is that 'pulling up is a myth'. I know this because my feet variously fall off/lift off flat pedals (eg if they are the slightest bit damp) unless I make a conscious effort not to try at all hard when riding my utility bike which still has flat pedals on it. I can just about keep a lid on it in the dry but only just. Pulling out of junctions and short climbs are still problematic; I've been mostly riding with my feet attached to pedals for about forty years and it probably isn't safe for me to (quite pointlessly) change away from pedalling nice circles. Flats on my utility bike are only tolerable because I don't do thousands of miles a year on it. I would therefore suppose that flat pedals may best suit folk who "don't try too hard"...?
Because you have trained yourself to do so, you have used some form of pedal retention because you have been told that it's necessary, and then when you have that equipment you have taught yourself to pull up. That is the habit you have got in. There is no evidence in the above that if we banned you from ever using pedal retention ever again, you'd be forever slower. The reality is after a few weeks of adjustment you'd be back to normal and just as fast as ever.
You've been riding with pedal retention for longer than I've been alive. Excellent, the thing is, the person in question from the OP, hasn't been. So the question is, should this person start. I'm suggesting no. If we were to transport 40 year ago you to now, and give you modern bikes, I would also argue that unless you are competing, then you don't need to worry about pedal retention, just ride your bike and have fun.
FWIW when you need a 'manifesto' to choose flat pedals and then go into ever decreasing circles worrying about the soles of your shoes, the exact degree of flatness, spikes etc it is in truth no simpler than worrying about cleats, clipless pedals and so forth.
I have no manifesto on this, I shared a link to something that actually came up in a different thread on a related subject on this forum. During the summer I've been wearing a pair of Salaman walking trainers, and now it's winter I've swapped to some Miendl walking trainers. I use Shimano M324 pedals, which have SPD on one side, and flat on the other. Why do I do this when I do not believe that SPD is necessary. Because a) I wanted to be sure of this for myself, thus needed pedals to try it. and b) I joined a group ride who gatekeep their rides by mandating that you must have pedal retention to join them. Which should have been a red flag, as it turns out that they were a bunch of total wankers, and I haven't ridden with them since. But it does mean I have the option.
I do have a pair of SPD-SL pedals in the box. But no shoes to go with them. I should probably just flog them.
Maybe I have weird feet, but I've yet to find any cycling shoes that are comfortable past the 3 hour or so mark.
Ultimately you pays your money and makes your choice. I ride flats, because I don't see any benefit for the riding I do of using anything else. I am not a roadie, I don't know if I fit any sub-category of cyclist. I ride a MTB frame, with TT handle bars, and road slick tyres. There's always luggage attached, and I carry a toolkit better spec'd than some bike shops. But then I'm also not out to be the fastest there is. I just want to go for nice rides, long rides, lots of them, day after day. Is it touring with a sense of urgency? Maybe. Am I pedalling endless perfect circles? probably not. But it's this road I ride... Maybe if I was cruising at something more than 20-23kph...
YMMV, etc.
I'm only interested in the reasons for people's individual preferences, and details of their own experiences. People are entitled to their own view on their personal requirements, even if they're based on misunderstandings. It's all entirely subjective.
I may have understated my friend's experience - he's done several rides of 100km+ using mainly (borrowed) Look Keo pedals, but also SPDs, so he does have some insight into the pros and cons of both. But he is still relatively new to road cycling and doesn't know what he doesn't know, if you see what I mean, hence asking for advice. And it was contemplating what advice to give him that made me realise my own experience of pedal systems is pretty narrow, which is why I was interested in canvassing for a wider range of opinions. I might have guessed it would lead to the usual pointless arguments. 
Anyway, since he gets on fine with the Looks, I have suggested he sticks with those.
What sort of riding is he doing? Does he just want to ride his bike and enjoy the ride? Or does he want to race? or chase KOMs or pretend he's in the pro peloton?
Answers to the above can define what pedals you end up with.
Depends on how many different types of shoes you want to combine with different types of bike, I suppose. I'm used to choosing between shoes, sandals and waterproof boots according to conditions, and while certain combinations are unlikely (I tend not to use the boots on the recumbent bikes), you're either limiting your options or justifying a whole load of s+1.
Not to mention the number of users of said systems, and the amount of space you have for storing shoes. If every bike is only riden by one person, then it's less of an issue, but if you have 2 riders who share a bike, then you now have 2 sets of every type of shoe, which adds up fast.
I have two pairs of SPD shoes, one I bought, and one I was given, and it's a faff to store them, They usually end up under a wheel in the hallway somewhere. I'd hate to think If I had to have multiple pairs for multiple systems...
J
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