Any insight into the qualatative differences b/w these two materials? I'm thinking of trading in my 06 Jamis Aurora (great bike, Reynolds) for a Cross Check (4130). I've read quite a bit on this forum about the perceived overpriced Surly products, mostly due to its "cheap" 4130 frame. Is the 531 superior? Equal? Inferior? If it's at least an even trade in terms of the frame, I'm doing it. Thanks in advance.