LogFAQs > #966182078

4, 5, and 6 give you a completely different set of bosses/allies and powers you get, which is pretty significant, but not worth playing both games for unless you really want to. It is a shame though because all the different bosses are fun and the fusions are fun to play with

3 was different - blue version was like a 'special edition' they released later in Japan but they gave us both versions. They're BARELY any different at all