It does seem that home grown are hottest. I know I'd been eating store boughts all winter, and was floored by the first home grown pods I ate this year.
I think this is probably influenced by 2 factors: Freshness, and cultivation.
I'm not sure how farming is done where most of the Habs come from here (Mexico) but I know that most local farmers have their plants on drip irrigation systems. This means plants are never deprived of water or the needed nutrients. The plants aren't stressed the way they would likely be in a home garden, and therefore don't produce pods to their peak heat potential.
Also, it's very seldom around here that you see store bought habs in really great shape. It does happen sometimes, but usually the stems are brown and withered, and the pods are obviously picked while not completely ripe. I often see yellow pods that are obviously orange habs that were picked green. Pods are often mushy, diseased, or just plain un-appetizing by the time they make it to grocery stores. The way I figure it, pods that look this bad must also be suffering from degradation of cap as well.