If I can find a reliably-feeding long gun, then, .45 Colt. My first try did not go so well, with a ‘92 Mirokuchester. My second try is with a ‘94 Angle Eject.
The damage done to my right wrist and thumb, in the Eighties, by shooting an S&W 629 with K/L-sized hands, has forever turned me away from any .44 Magnum.
An easier poll choice, for me, would have been .357 Magnum, for which I have a Ruger No. 1, a Browning ‘92, and several Ruger and S&W revolvers.