Yes, difficulties make a difference, at least in the PS2 version that I ran. Primarily, it doesn't really make the AI more competent in my experience, but it does increase their damage output pretty noticeably. As such, while you can tank bullets on Easy, thus allowing you to speedrun more efficiently, just bringing it up to Normal means most "tank and run" strats that work on Easy will get you slaughtered on any higher difficulty.

I'd agree at first that if difficulties are added that they only be for IL runs, but I'll defer that to anyone who has actually run the game on the higher difficulties (Hey, @Rathin, you have thoughts on this?), because SH2 isn't even my bread-and-butter speedrunning game; AA2 is. I just started running SH2 just because I had the game and was already in an Army Men mood, and because I never actually beat SH2 100% as a kid and wanted to finish my unfinished business.

Hey, Skilloz. Can you add a PS2 category on the "Level Leaderboard"? Since, as you know, the PS2 version is rather different from the N64 version (and, actually, different from the PSX version too), these are the levels in the PS2 version:

Boot Camp, Dinner, Bridge, Refrigerator, Graveyard, Castle, Tan Base, Revenge, Desk, Bed, Plasticville, Toy Shelf, Cashier, Toy Train Town, Rocket Base, Pool Table, Pinball Machine.

As of now, I've got one run of Dinner recorded: a 1:19 IGT. I'd like to submit it and might attempt to do the other levels.