Well, if you are looking for power, Chrono's Luminaire, Lucca's Flare, and Magus' Dark Matter (that was the strongest, right? It's been so long...) are the best. Marle/Nadia is good for healing, but I never use her 'cause she's a pansy. Ayla has some nice moves, and the first time through the game her and Chrono's Falcon Hit double tech is really helpful. Frog/Glenn is all right, I'd only use his healing and his physical, I have yet to be able to use frog squash to a great effect. When my characters are weakened, I heal, not attack. Robo/R66-Y is pretty good, I like his combination of healing and offense. Personally though, I feel Chrono and Magus are the best, Chrono because of Luminaire (and Confuse and Life) and Magus because he can use all elements, especially Shadow.