Noel as Commander and Serah and Rav. seems the default choice. After a bit early into the game, felt a bit boring controlling Noel as Com main, so I restarted and have Serah as my control/com and noel as rav. It feels different and having fun with it right now.
Hentai = Art Pokemon: 2580 3015 2189 "Its all about love, friendship and courage! - Laguna, FF8
Well, you don'T need to restart in order to make Noel your Rav and Serah your Com. Ruin's strength is determined by Serah's magic stat. While Noel learns Rav spells that are based on his strength. I played the game in german, so I don't know their english names. The spells he uses by hitting enemies with his swords. [insert Element Name here] Hit?
I'm not sure if it's possible to give Noel the highest magic stat, though. But if there is, I'd like to see the instructions. After receiving Com Lightning, Noel only worked as Ravager from that point onwards.
More towards end-game and most of post-game, I start using them as either COMs or RAVs in the same paradigm. But if current battle demands allow me to, no, I would much rather like to use Noel as my COM and Serah as my RAV.
A COM that just uses Ruin all day is just too damn boring, and trumps DPS freaks' love of extreme efficiency by a milestone for me. Also, Ruin doesn't trigger Launch, Scourge, and Smite. I'll admit if you keep up your crystarium progression, much of the game can be done without those abilities, but it's good to know that if you're going to make use of them, a strength COM will be doing so and won't waste an ATB segment on a minimal damage Launch attack or if timed right, a Scourge without buffs/debuffs.
Again, towards late and post-game using two COMs or RAVs at once is probably better but I just happen to like more variety in my paradigms if the story allows it.