Serious answer to original question:
I've been playing A15 lately. I would play A14, but on Linux the graphics/lighting is screwed, and TFP never fixed it. So A15:
I prefer the old level/skill system. I've spent a lot of time with both, and miss the older version.
Spam Crafting! If I make 10,000 axes, you would think I would get good at it after a while. The level of my axes reflect my increasing skill in A15.
Hub Cities! Yes! Hub Cities! Need I say any more?
Lootable Zombies
Giant Bees - annoying but not as annoying as buzzards. I actually like buzzards too.
No health/stamina caps, no encumbrance. Those just annoy me.
Book Stores with recipes. Real recipes.
Recipes that you can read more than once.
You can run backwards, I think they finally removed that in A17
Dogs are harder to kill. Why do I miss this? Because dogs are stupidly easy to kill in A17. You bonk them on the head once, and they sit there, stunned, while you walk up to them and kill them. In A15, the dog runs up to you, rears, claws you and unless you move fast or put down spikes or barbed wire or get off a good head shot, your gonna take damage. Dogs are much deadlier in A15.
I think I started with A10, and while A10-A13 was OK, A14 was when they reworked the inventory/crafting display system, and while that was great, they screwed the graphics/lighting on the Linux client and did not fix it until A15. In A16 they introduced skyscrapers and removed the hub city. Hence my preference for A15.
A15 is my chocolate ice cream. I understand not everyone likes chocolate. I do.