For me it depends on the game and character. In games where people have specific classes I play according to the class. In games with switchable job classes I keep a balance between magic and physical users unless a specific boss or dungeon calls for something different. In VII I think I went almost all physical with the occasional summon, but I had Aeris act as a white mage and tried to make Cait Sith a blue mage, but it was difficult and with blue mages I most of the time just end up using their physical attacks majority of the time. In VIII just about everyone was physical. I had Selphie and Rinoa as my magic casters though. Selphie seems to be pretty weak in physical attacks.