Won three of the four "pump gun only" Sporting Clays shoots I've entered ... and don't find the pump a handicap whatsoever for most shooting. The single choke can be a bit of a setback with demented target setters, however, if you're on - you're on !
I wouldn't neccessarily pick a pump first for the recreational target Sports, but Sporting, 5-Stand, 16 yard Trap singles and Skeet at the Club level aren't problematic. Tougher courses and competition ATA Trap/Doubles, International Skeet and International Trap, is almost all "first choice O/U", as is English Sporting & FITASC.