Good question IceAngel: I say so because I actually wrote out a list of pros and cons, abilities and junctions, etc. during one play through... 8-B

These junctions are interchangeable between characters:

first: Quez., Ifrit, Leviathan, Cerberus, Eden

second: Shiva, Siren, Diablos, Pandemona, Tonberry

third: Brothers, Carbuncle, Alexander, Doomtrain, Bahamut, Cactuar

Of course, this set up works much better after you get the majority of the GFs. Until then I'll spread it out as needed. With this set up(excluding a couple of exceptions), everybody gets all of the main junctions: HP, STR, SPR, etc., and you also need to get fewer GF ability items to teach the extra stuff. I don't worry much about compatibility, because there aren't many instances when summon speed is absolutely critical, and, also, I always do the card quests so I always refine the 100 Luv Luv G's from the chubby chocobo? card, which is instant 1000 compatibility with your three main characters.

Yeah, and I hate, after getting everybody junctioned and all the magic where I want it, having to start all over again because I had to go on a flashback with Laguna. (I know this is avoidable, but I usually forget to junction the right people so that it transfers from present to past.)