I'm a fan of streamers for stocked trout. Rarely get the chance to fish for wild fish, just a few times a year, so I'm mainly using dries for them, though I'd like to try big streamers for wild Browns sometime soon. Steelhead are another fish I feel would respond well to meat flies, but, in most of those Tribs you'd snag one with a hook that big before you even started stripping in lol.
Anyway, I use streamers as small as size 12 (skittish fish) to as large as a 2/0 for the fiesty fish. I find the best size range is 2-6 for most PA Trout. Lakers are a different story and I just started fly fishing for them, no hookups yet but a few follows using hooks from size 2 to 6/0.