Why would you ever use the ATI player? Ok, it can play the VCR files and can use FF/RW when some other players can't. But really, it stinks. I don't like MMC at all really. I mean, it works, but it's a usability nightmare.
Because I own the ATI Remote Wonder, a 27 inch PC monitor, and a Windows 2000 PC equipped with a All-in-Wonder Radeon card. I don't feel like getting the remote to work with other software, because of the pain already present in having to reset my button preferences every time ATI decided to release a .1 MMC update.
iPhoto, I haven't had problems with. I have about 800 photos in my collection right now, and it seems responsive enough. Guess I have never bothered to look at much else, since iPhoto also saves me a bit of time with not needing to manage the files from my camera.