I've tried both, and own the Sirrus Sport. I personally found the Sirrus Sport to be more agile and fun to ride. Better looking too. The Sirrus Sport is very close to a flat bar road bike.

The downside is that the Sirrus gets a bit twitchy if you add a rack and load it down with panniers. It's fine if I use a backpack, but panniers are out. If you plan on doing the whole rack thing, go with the Trek.