IME, with the same layout and surface preparation, the Revolver will react stronger to friction and have a sharper change of direction than the Lethal. The Revolver will also have a few more feet of length than the Lethal.
For me, the Lethal works better on conditions where I want to play more direct (say, to bump an oil line), while I'll use the Revolver when I can give the ball more room to the outside (to hook around a push spot, for example).
Hope this helps.
Ray Salas
Brunswick Amateur Staff
http://www.brunswickbowling.com