Definantly ps3. 2 very good reasons for me would be very reliable in-game voice chat and the fact that the ps3 can use usb/bluetooth keyboards and mouses means it would work like the pc if u want it to and blizzard programmed it correctly. Also there is already the ps3 keypad wich could do wonders in a game like that too.
My PSN Name is: EvilChronos add me if u want :)
END OF GENERATION PREDICTIONS "9-21-08"
PS3=130M 360=90M Wii=120M DS=130M PSP=70M
Other Prediction: The PS3 will overtake the 360 XMAS of 09 "9-21-08"