On longer shots the 7 1/2 trap loads I used to use would only break the near side wing. They'd go down, but mad, and would run when they hit the ground. High-base 6's out of a modified choke would clobber dead anything I thought was in range to shoot at, including up through leafless tree branches.
At closer ranges the 7 1/2 would do fine (when coming to the call and going overhead not too high). On higher or farther pass-shooting kind of shots I preferred the 6's.