After 1.6 the game lost "that feeling" 1.8 is when nunuMinecraft went into full swing. I'd still say 1.7.10 is my favorite because it has lots of mods.
Besides that, I understand what the beta 1.7.3 crowd is getting at, even doe I first played Minecraft at 1.4 release. After that update, you can just sprint past the mobs, and you have to hold right-click every three minutes. Better Than Adventure looks like a nice mod even though it's trooncore and I haven't played it yet.
My second and third favorite would be the Nether Update and Caves and Cliffs. Those were too high effort to dislike, personally. The update where they overhauled oceans, changed swimming, and added coral gets an honorable mention.