well, first, the V2 is only 3D, and runs great on glide but resolution CANT be higher than 800x600. A 2x V2 12MB in SLI will boost performance.
For the Banshee, it is more recent and have some more fonctions/more ram, is both 2D and 3D and can go to higher resolutions. But the only problem with Banshee is that it doesn't support mutli-texturing ( due to single TMU) so in some games, some effects won't show correctly. Like the sky transition day/night and the flames in the Zelda games and other stuff.
In fact you have choice, both card has pros and cons. it's to u to select what you prefer most/or what you don't care about.