Biggest difference between the Crosstrail Sport and the Sirrus Sport, would be the fork, one has suspension and the other has a carbon fiber fork(which I know, it was obvious). The other big difference is really geometry. This is where you need to test ride the bikes to find what fits you well. You may end up testing both of these and can't stand it because it doesn't fit you. Where as other bikes might fit you better. Tire size, pedals and other things like that are easily changeable to meet your needs on both bikes.

You stated that you will do mostly pavement riding. I would suggest the Sirrus or other brands without the suspension then. I got the suspension mainly because I ride alot on paths like the Chesapeake and Ohio canal that I feel the suspension works...ok. The suspension does add weight, which does lessen the feeling you have when riding. It doesn't have any maintenance, or at least my LBS is telling me so. If it does, mine is going to die a horrible death then the way I've been riding it the last two years.