Longsword all day, every day.
Eh. They were prone to be noobish in Tri, but now it takes some skill to get decent spirit combos. (I guess that won't stop the noobs from using it, though...) I can't say I ever liked using the LS, except against Ceadeus.
I still expect Dual Blades to be the most used thanks to quick attacks, flashy effects, and element/status combinations.