Couldn't tell you which is "better". I have one unfired 452 FS, and six - yes six - 455's. I own three Canadian 455's - 17, .22lr, .22wmr - plus three Americans - same deal. I didn't buy them because of the barrel change feature, but mostly, I suppose, because the 455's were nice looking rifles. IIRC, I bought the 452 FS first, then I was hooked. The .17's are both wickedly accurate. They even make me look good! 
edit: I may have to scout out a nice 455 FS. Only makes sense.
edit: I may have to scout out a nice 455 FS. Only makes sense.