if you want a bike that will 'last', don't buy carbon fiber.
I'd go for a trad steel Trek 520 at your weight, but hey. why the portland and not the 520? the 520 and the tricross are more comprable bikes than the portland and the tricross.
Regarding carbon fiber in bikes, the Consumer Product Safety Comission will be doing a major review of their bicycle standards in 2007, partly due to the proliferation of carbon fiber in the bike industry; expect to see heavier carbon fiber componentry in the coming years and more weight limits.