I looked into these EXTREMELY thoroughly. I've decided I'm saving a few extra pennies and going with stick-built w/ trusses and regular composite shingle roof.
Several reasons--
* In WA state (I don't know about OR), ANYTHING covering more than 200sq' of ground requires a permit. And they were VERY clear on this - anything over 200sq'. Several of these metal carports are on sale "used" on craigslist because the owners did not get a permit, and got caught and red-tagged.
* To get one of these permitted required engineered drawings, 12ga metal instead of 14ga, and approval. Almost doubles the cost. I priced a 26*24 @ around $4k for it to be legit with a permit.
* Stick built raises your property value
* If you do go with metal, go 12ga and not 14ga, small price but much better durability and warranty. Likewise, go with augers and not the base-price rebar rods. One good wind storm and over they go.
Stick built, legit, and permitted for me will run around $9k from the bids I've gotten so far. That's on 6x6 posts, beams and engineered trusses.