1.7. Because mods. 1.7.10 has the largest number of good ones, but 1.12 has enough exclusive ones to be a rather annoying. But there are things I don't like about 1.7: the Nether. I don't know why I don't like it, but there you are. No lapis for enchanting. Yes, this one makes things more convenient, but this makes lapis practically useless except for dye. No end cities!
My favorite updates are 1.13-1.15. Why? Because 1.13 updated the oceans so that they were full of life, 1.14 because they updated villages and added a new level of excitement with raids, and finally 1.15 because of a few major bug fixes, dispenser changes, and bees.