I was thinking of dedicated data loggers, which will save bulk and power by not having a user interface.
After a couple of Garmin issues recording for DIY Audax, I've recently bought a USB GPS logger as a back up
https://www.amazon.co.uk/Canmore-GT-730FL-Rechargeable-Waypoints-Compatible/dp/B002UWKUZQ/ref=sr_1_1?s=sports&ie=UTF8&qid=1483347268&sr=1-1&keywords=gps+data+logger
I reviewed it elsewhere:
The instructions are in a form of translated Chinese which was common in the 80s, it takes a couple of reads to get the jist. Software is supplied on CD, but the review I read said the most up to date versions are downloadable so this is what I did.
Played with it on my commute and a couple of short club rides, works fine and really straightforward. Switch it on, power LED lights up, starts flashing when it has a fix (First time took 5 min, less than 1 each time after) end of a ride switch it off. Plug it into the USB, import the track to the program, export in whatever format you need (GPX in my case) You can change the recording frequency in the same program, I've left it at 1 sec for now, which has a run time of 17 hours. My longest track has been a 13 hour 210 km which used 6% of the storage. It doesn't have a battery level gauge, but it will run plugged into an external battery.
I haven't used the geo tagging function yet, I'm not sure it's something I have a use for, though I might have a play with it anyway.
reliability is the crucial thing of course, too early to know about that, but so far it's been as expected and I'm pleased with it.