I believe the difference is whether the fasteners are exposed. In one case you have hundreds of holes in your roof and depend on something like a rubber washer to keep the rain out, in the standing seam the fasteners are under the roof and as long as gravity works you should stay dry. I mostly see the u panel on utility buildings, not houses in New England. I'd expect the standing seam to last much longer-- I doubt a warranty is worth much 15-20 years out.

24g is also thicker or better quality than 26g.

From what I was told by Mueller when I bought my roofing materials was that it is asthetics. The standing seam looks better with hidden fasteners but takes longer to put up. The upanel (or rpanel) goes up quick. We ended up with rpanel as we were on a very tight budget. I wished we did standing seam.

Do these prices include labor? I was told standing seam vs rpanel was about 10-15% more materials wise but labor wise would be quite a bit more.