Oh nothing major

its just that they belong to diferent turtle familys, genera and species, and they have almost no similaritys apart from their comon name and the fact that both are turtles. The indian spotted turtle
Geoclemmys halmitoni (I hope the name is spelled correctly) is a tropical protected species and it cant cross state lines. Outdoor keeping outside of Florida is a big no-no. They also get huge and are very expensive. The spotted turtle
Clemmys guttata is a good species in a outdoor setup in northern climates but its also a kind of tricky turtle to keep. Some report their easy some say they are dificult, I say try first with a hardier one before these. Also they are protected in most of their range and they may even be ilegal to keep where you live so check your regulations.