The Desert Eagle is awful. It looks bad and it shoots badly. Mine was passed on quickly. I am not a fan of the fake automatics so I would go with the S&W if you can live with the cylinder.

I much prefer BBs in a CO2 gun though. Less accurate granted, but more fun and power is not something you should worry too much about with the majority of CO2 pistols, just concentrate on having fun.

EDIT: In answer to your title question, I don't think there is a "best" CO2 pistol, but there are many that people prefer.