Lets see I would rate the "Steel Buildings" as
BEST to ......"Less Best"

red iron building ( most commercial buildings are made this way)
A hybried building ( some type of metal "web" trusses and then wood for the purlins and girts)
A Pole building ( wood poles, girts, and most use wood roof trusses for a clear span)
A "Quansit hut" <SP?> type ( most look like a half of a large culvert pipe, But there are modified types that have straight walls too.
I built a red iron building and I purchased it from
www.steelbuilding.com Are they the greatest?? no. Would I buy another from them?? yes I would.... What I really liked about them was no scuz ball sales person pushing some scam. You design the building and if you like it you can order it w/o even talking to anyone if you want to. However their people will answer any questions you may have. The down side is that you will have to arrange the errection of the building, they will not come out and put it up for you.
You can see its construction in the link below.