Well, jere's to my first post on these forums

Well, I'm going with the four member party, but I'm picking enough charachters for a two party split (in case I have to fight Sephiroth ).

My main pary will consist of the following:

Main (a.k.a. Cid is a Pimp) Party

Cid Highwind (vii) For your general Dragoon type buttwhooping. Especially since his Highwind Limit break can do over 200,000 points of damage
Rikku (x) Thief/Chemist & Copycat. Also, once you're done with her part of the sphere grid, you can teach her all sorts of magic. One of my most-used charachters in FFX (until I was able to teach Kimarhi and Yuna the steal and use abilities, then my gil farming/item plundering increased exponentially)
Yuffie (vii) Thief/Long range death, plus with the Oritsuru or Conformer her Doom of the Living Limit did almost as much as Cloud's Omnislash.
Aeris (vii): Sage/Summoner. High spirit and Mind stats give her a ton of MP and a higher damage rating to all her spells, plus her Great Gospel limit break got my butt out of several jams in FF VII. Never underestimate the power of party-wide invulnerability.

Alternate party:

Cloud (vii) All around butt-kicking, and Omnislash > j00
Zidane (ix) Thief and, if you equip "thief swords" major damage dealing, especially with his Formula 9 trance. I whupped Kuja (first fight) by having Zidane go into trance and using that attack on him 5 or six times.
Rinoa (viii) Long range damage and high versatility
Garnet a.k.a. Dagger (ix) WHM/Summoner. General support and summoning + Holy.... Don't leave home without her.