I like to commute, to tour, to ride fast sometimes, and ride roughstuff.
I have several bikes, but I keep returning to my Orbit. It's not as fast as my Woodrup, it's not as classy as my Carlton, it doesn't have the vintage cachet of my Rudge, and it's not as well suited to a commute as my other Woodrup frame will be when it's built
But it does all those things very well. I can burn off some carbon boys from the lighs even though I have front pannier racks. And, if I see a muddy bridleway, I can just peel off & go. No worries about whether the frame can take it (it's 531ST).
So, if you're going to go for the one all-rounder bike, I'd recommend you invest in a time machine, go back about thirteen years to before Orbit moved to Sheffield, and get a Silver Medal (but do, please, change the Selle San Marco Fox saddle for something that can actually be sat on).
The only niche I can't fill with the Orbit is tandem. And we have a Super Galaxy that does that nicely