I've never shot an AK-74, but I have an AK-47. From what I hear, each have thier pros and cons. Alot of it depends on the round. That's probably the biggest difference between the two rifles. 7.62 has more recoil, and packs a bigger punch. 5.45 has less recoil, but isn't as powerful a round as the 7.62. I think the caliber just depends on your preference, because I think they are pretty much the same rifle. My AK is a WASR-10 in 7.62. Ammo is cheap and plentiful around here, and recoil isnt really an issue with me. I love my AK.
But, again, that's just my opinion, and what I've read around here. As I said, I've never even laid eyes on an AK-74, let alone shot one, so I could very well be wrong.