Vincent.

For me, there's no contest. Although they're both gun-wielders, they fall into different categories in the Final Fantasy archetype system: Vincent is the broody mysterious one (such as Shadow from FFVI, and Kain from FFIV), while Balthier is the CHICKS, CHICKS, CHICKS! type who womanizes to hide his homosexual tendencies (such as Edgar from FFVI, and Irvine from FFVIII).

While I still like the womanizing characters to some extent, they still have lots more lamery than the brooders.

Vincent, although you could also have had Irvine from FF VIII on this list. Even then I'd still go for Vincent. He's awesome. Especially with Chaos.

I prefer Balthier a little bit more than Vincent because emos don't appeal to me.