Go with the light 2 3/4" for sure. 3" shells may not even be allowed at some places as they limit the size and power for the sake of targets and ears. At any rate, you would get tired in a hurry in an 8 round shotgun stage with those heavy loads. I don't shoot 45's but with 38's the heavier bullets tend to be a bit more consistent while the lighter bullets kick a little less.
Good luck and good shootin' , griz