I switch leaders between Lightening and Fang. For farming I use Fang always, as you said for high wind. Taking out the legs of a Adaman(tor)toise is so easy with Highwind.
For length boss battles (Mission 64 for example) and getting the chain bonus up when you can't really use Tri disaster, I'll always choose Lightening as party leader. All depends on what Im doing. But I never choose anyone other than those two.
Lionheart upgraded to Omega Weapon for Lightening for Quick Stagger. It's Synthesized Ability for Instant stagger with Energy/Speed Sash's is amazing. I beat Gigantaur really early due to that.
Pandoran Spear upgraded to Kains lance for Upgraded Debuffs.
I think I upgraded the Hawkeye for Hope. Don't ask why as I have no idea, didn't think about it when I did it stupidly.
Belladona wand upgraded to Nirvana for Vanille again for added Debuffs.
Paladin upgraded to Save the Queen for Snow as I only bring him out if I plan on using a Sentinel for an entire battle.
Can't remember Sazh as I barely used him, which is pretty stupid of me as he can be extremely powerful if used correctly. Ah well.