I learned on French and played it exclusively for about 20 years. A couple of years ago I got curious and bought an inexpensive German bow (thanks Don Z.-- it's still going strong!).
It was slow going without a teacher, but I'm just now starting to approach being able to do with the German what I can do with the French, articulation-wise (spiccato, tremolo, etc). I did used the German to play a show recently (Sweeney Todd) that required a lot of low-end power, and I found that I was able to pull a somewhat bigger sound for those E and A string fortissimi (?) and had better endurance than I would've with the French.
Also, I've been using the German to play arco solos on jazz gigs, and for some reason, I feel more comfortable with the German in that situation. Probably just psychological -- the PC mojo or something.