I play on all from 1.7.10 to 1.15 mostly these days (beta to 1.6.4 if I feel like it but not as often) depends on the mods I'm using that draw me back/videos I'm making and haven't played in survival consistently in a while but I'd say I'd commonly play on 1.7.10, 1.10.2 or 1.12.2 if it weren't for video making on mods or datapacks that I mostly cover in 1.13 and 1.14. But as I'm in 1.14 a lot these days I'd have to vote 1.14.
Otherwise I mostly jump to the next version mods do, been doing it since 1.8 besides just jumping from version to version for Vanilla reasons prior to 1.8 as far back as starting on 1.4.5.
1.6.4; I've never really played on any later version (the most recent version I've run is 1.13 to check out claims that cave generation was changed) and basically make my own mods to add in my own "updates", as described here (not that I have any problem with vanilla, some of the more annoying bugs aside, including some still not fixed in the 1.15 snapshots; my playstyle is pretty much the same in a (basically) vanilla world as my more modded worlds).
I play on 1.10.2 currently, so I will vote for that one.
Why? No specific reason to the version itself. It is simply because any time an update requires changes, especially to resource packs (I'm not sure 1.11 did, but 1.12 did for my texture pack), procrastination sets in and I usually stay with a version for a few versions worth of time. That's because they change often (and this isn't a complaint; more the opposite as I have deep gratitude to those keeping the John Smith Legacy resource pack updated, maintained, and hosted), and I am picky about it staying as close to the same as always, so I usually download the latest version as a base, then invest time and such changing it back to how I wanted, which is more work for someone like me who doesn't know what changed, what was renamed, why something is looking different color-wise, etc. One version may have custom colors breaking (this was a big roadblock for 1.7 with me), another requires me to go and dig in and find all the ones causing connected or random textures to be forced on since OptiFine's option doesn't work since the base game now supports/uses it if it's there, another version changes biome colors, etc., etc., etc.
Not only that, but while my list of mods isn't large, I always would at least wait for OptiFine, Forge, and Better Foliage to update as well. The game feels so sterile to me without that last mod, and likewise, I'm so glad someone put the time and effort into "remaking" that mod starting with 1.7 when Better Grass and Leaves didn't update past 1.6. I'm so grateful to a few in particular. Anyway, if it's something like 1.7, 1.8, or 1.13, all of which had huge performance penalties and sometimes other large changes (like massive resource pack overhauls), that goes more so.
I wanted to update to 1.14, and was going to since performance is actually slightly better than 1.10 (1.13 was way worse), but I'm running into other issues. I feel like putting work into moving to 1.12 would be wasted in case I can overcome the issues I'm having with 1.14, and in the meantime I'm more interested in working on my builds/world, so... procrastination sets in and I'm "stuck" with 1.10 for now.
I am playing on 1.14 and might stick to it until another village update version appears or until additional attractive biomes are added. I‘m not interested in bees or the nether, so I‘m not convinced I should migrate my world to 1.15. I‘m still considering it though, depending on which bugs are fixed.
I play on the last release - 1.14 (.2 to be specific), I don't quite consider 1.15 to be a version yet until actual release, I don't count pre-releases. I'll probably be sticking with 1.14.2 for a while as I see no reason for me personally to update so far. Like Toadrunner I don't care for bees and honey blocks so will be skipping this next release as it holds no interest for me. The Nether update does interest me though, greatly so and way more than bees and honey, although it's doubtful I will upgrade my main world to it as I have nether routes and stuff I want to retain as it is. I'd rather make a new world for the new nether.
I also am happy to wait for biomes, and not just the mountain update from this year but, the other ones they've supposed to have added by now. 1.14 has the benefits of the update aquatic for me from 1.13, and while the village and pillage update can be cumbersome, there is plenty more me me in terms of blocks and stair varieties, campfires, barrels, some (Not all) work stations and of course bamboo for scaffolding. Plenty of reasons for me both building and crafting to update.