I think the A600 *may* be more compatible with older games, however the A1200 works the majority of games anyway, plus alot of the incompatible ones can be made to work by some tweaking in the early startup menu.
Plus I think the A1200 has a faster processor. more memory(?) and it has AGA chipset, which is required for some good games and programs. Personally I would not go for the A600 unless you also want portability nad *cuteness*
