About GTA V's AI... there is none, GTA V has no AI at all, no pedestrians have common sense or pathfinding abilities, look what happens when a car hits a wall, it reverses a tiny bit, and then hits the wall again, and again, and again... Pedestrians don't know where they're going, they are bland, boring, hate you for no reason, and are so sensitive to the point that they get scared from you falling over (the whole block will start screaming). You get in trouble for doing anything, accidentally bumping a pedestrian automatically gets you 1 star, standing near a ped gets you in trouble, it's not fun at all, and shows a lack of proper testing.
GTA IV to me showed more of a realistic world, you could go around and admire the city without getting in trouble for no reason. The wanted system in GTA V is a joke, cars and helicopters spawn right in front of you (I'm not joking, they always do), they have horrible rubber banding which causes them to crash like crazy, and always know where you are (okay, GTA IV had this problem, but you would expect them to fix it).
I didn't like how we got thrown a half-done single player experience, in favour of that online mode they made, it's unfair to leave us behind because single player won't make them more money. In GTA IV you got everything you could. So, until GTA V comes out on PC and mods fix all the problems, as well as a trainer to let me get all the exclusive and online stuff, GTA IV still shows a larger amount of care taken for it, with the story, the map, the characters, etc... Hey, at least you could go into buildings in GTA IV, unlike GTA V and its 3 or so different copy-pasted shops and pointless, empty banks that do nothing.