Where are you going to ride it?

I've had both Cannondale Aluminum bikes (T1000) and Trek 520. I like the ride of the Cannondale better and had ridden it across the US (twice) and across Canada (once) and a bunch of other places. While riding the perimeter of Australia, I had the frame crack and so I picked up my other Cannondale T1000 to complete the circumference. After that for my next big trip, across Russia, I rode a Trek 520.

So for most cases, I would pick my Cannondale because I like the ride better. If I do a more extended third world tour, I'll take my Trek 520.