Hm. Hard to say. I suppose it really comes down to...
Griffin vs. Qudssi vs. Rajav: All have roughly the same role -- melee attacking and tanking. Qudssi is very useful at the start for his high skill, speed, and mental resistance, but his specialization is too narrow. Griffin outclasses him later on, due to having more versatility. So it's really down to Griffin vs. Rajav in the endgame. In terms of tankiness, they're about evenly matched; Rajav has physical resistance, and Griffin has a counter-attack. It's hard to say who's better offensively; Rajav has a ranged attack and an (arguably) better area attack, but Griffin is better in terms of pure damage with Backhander and Double Strike. I generally go with both, to be honest.
Arman vs. Malis: It's a real pity, since I like shadowlings and Malis is the only one, but I generally find Arman to be better. He has a better damage output, and better speed. The only thing that Malis has over Arman is flight...and I guess shadow resistance? Eh. Doesn't do it for me.
La'Man vs. Naj: Naj, all the way. She has better speed and Mind Shield. All that La'Man has over her is a touch of extra health, but Naj is already a decent tank.
And I guess I'll do a numbered list thing, since everyone did that in the corresponding TRPG2 thread:
1. Rahel: Definitely one of the more valuable team members. She has the best range in the game, and can deal significant damage. Great for staying behind the main force and sniping enemies. Split Shot is really useful, too -- it's like Trick Shot, only better -- I didn't think that was possible!

I was little disappointed to discover that Trueshaft was just a "deal more damage" skill, though -- I was hoping she'd get a skill that shot 4 spaces ahead, to give her even more range.
2. Set: A healer, and a good one at that. Invaluable, even if he can't damage enemies directly. Solid State Shield is pretty nice too, though I didn't get it until my second playthrough, which I'm still on, so I'll have to experiment with it a bit more.
3. Luca: I really like her, for no other reason than I love characters with weird, gimmicky abilities. Transfer is a godsend for me, since I'm a fan of high-cost abilities; most of my characters eat through their PsP like popcorn. Her physical resistance also makes her a decent tank. Also, she can fly -- always a good perk.
4. Griffin/Rajav: As I mentioned, I find that they about tie in usefulness.
5. Arman: He dies too easily! He can deal a lot of damage before he goes down, though. I think a ranged attack would have been really good for him -- allow him to keep his distance a bit. Or would that have made him too broken? :p
6. Naj
7. Malis
8. Qudssi
9. La'Man
To be honest I found the team diversity to be a little disappointing compared to TRPG2. It's mostly just boring humans.
Edit: Hm. It would be interesting if the poll showed team combinations instead of the individual team members themselves. Ah well, the limits of technology...