I use Sam's because it is much closer to my home and I have always enjoyed the results. I think their meat is good and generally use it when I compete. Here in St. Louis, Sam's always cuts the butts into pork steaks but, if you ask, they will bring you full butts individually or in 2-pack cryovacs. They also slice up the Tri-tips but will always accommodate me when I ask for a whole Tri-tip. I wonder if geography plays a role in the quality of the meat?
I have had only one experience with Costco, in 2004 at the Royal. The butts at Costco were all boneless and didn't turn out well. The ribs from Costco, however, scored very well.
Mark - Roadkill BBQ