Basicly SA2 Battle has graphic "upgrades" like rain in White Jungle, and a better Chao system with the inclusion of Chao Karate. There are more levels available for 2-P mode, and all the 2-P characters that had to be unlocked in the Dreamcast version are immediately available and each character was given their own stats. Also, some of the high-score requirements for A ranks have been changed. Otherwise it's the same, oh, and some different enemy placements.
~ SA Tails & Crazy C Lea