I believe the steel is about the same.
Buck, Case and S&M (Queen), all use 420HC and just from my personal observations from using knives by all 3 I would rank them:
1. Buck (hands down, their heat treat puts them well ahead)
2. Case
3. Schatt & Morgan/Queen
S&M/Queen, of the knives I have had, just seemed very soft and did not hold an edge that great.
TLC, do you have any experience with the Canal St. Cutlery 420 blades? I don't, and I've heard mixed things. Some people say they perform pretty well.