BART, I own a .450 Rigby, so I might soound bias, but given the above choice, as a general purpose gun, the .450 kicks serious ass. I have shot numerous shots at wounded game on the wrong side of 200 yards, and hit them with regularity, to reccommend it whole-heartedly. I do a lot of elephant safaris every year, so have been looking at various .500 doubles also, but I can tell you also that I would probably prefer a .375 CZ above a Searcy if my client/ staff and own life has to depend on it... If you decide on a double, make it a Heym, Verney Carron, Krieghoff or Merkel IMHO. (There may be more OK doubles, but a Searcy aint one of them...)
Sorry Butch, just my experience on the few that came through my camp. There is of course 1000's of people happy with them...