I kind of go back and forth (since I'm of course NEVER indecisive
). I like the deeper sound of the viola, and the fact that it's a little bigger than the fiddle (which is sometimes a good thing and sometimes bad), but viola usually plays either harmony or a classical version of backup, but not nearly as exciting. The fiddle I think is a little more versital, and is a little more fun. It's a bit more challenging, but I just love the treble sound of it, and all the different things you can do with it. It usually is stuck playing second fiddle (pun intended) to the guitar and the piano, but you'd be suprised all the different things you can play on it. But then, everyone needs a violist, so if you play the viola you're essentially a shoe into any quartet or strings ensemble on the face of the planet. So it balences out.