Maybe "route" is a regional difference. In any case, I've heard it pronounced one way, just as much as the other. I use both, myself, without really thinking about it.
Hawkmoon, how do you pronounce "route," when used as a verb? How about "router"?
When I was in the army, we used the phrase "in rowt" (phonetic spelling), to mean that we were on the way. I always imagined that it was spelled "en route," and it seemed like it must be French. So I sometimes pronounced it "on root." I don't speak French, but that was my best guess, and it just came out that way. Folks found this amusing.