Haven't played in over a year. Should I play Civ 4 or 5?

I have not played Civ in over a year. I cannot decide between 4 or 5? I like 4 because you get to pick your leader. Also which AI would cheat less 4 or 5? I'm thinking about Civ 3 in asking that.

You ask that in CIV4 forums?

These CIV versions are so different from each other, that many civ fanatics call civ 5 an epic fail, while the rest oppose, that huge changes in gameplay are refreshening.

If You fancy civ3, civ 4 is a somewhat of similar and You should definitely like it too. I personally like, that civ4 has a more civilized mechanism instead of nasty corruption for game balance. I also like megastacks of armies (civ 5 allows only one unit per tile). So for me, civ4 is definitely more attractive.

I recommend warmongering and the tourism mechanism/culture victory in civ 5 bnw; but other than that go for civ 4. Diplomacy, micro managing, etc. is better in civ 4.

If you like a peaceful builder game and an opening exploration phase with a genuine sense of wonder and discovery, Civ V. If you like battle that is not spoiled by overpowered promotions, pathfinding that works, and Antonin Dvorak, Civ IV.

They are really totally different. I have been playing all of them for years, and I got between depending on my mood. I would try Civ IV first, only because it feels strange to go a much older game after playing a new game with great graphics like civ V.

Thank you for all the replies. I think I will just play both, and a bit of Civ III for nostalgic reasons. It is true that each one is different (to varying degrees) and each has its own appeal.

P.S.
Civ Rev 2 is on sale for iOS (and Android) so now I even have Civ for my iPhone. I am not sure how long the sale will last but at US$4.99 I could not pass it up.