Between those 2 I'd use the 8 weight for sure. The only one I've caught was on a 3-weight blind casting to some bass with a level leader of 4 pound mono, but it was purely random -- I had no idea he was there. I'd be happy with anything 5-8 weight for them most likely. He was a pretty small one though.
Like Remick just said, they seem to be pretty "aware" of disturbances and don't seem to bite readily if spooked, or even mildly suspicious of your presence. I've taken shots at probably 15 or so this summer and haven't hooked a single one....though one a few days ago rose up to a giant popper I was using. He turned after he came literally 1" from it. Dernnnn! Maybe the key is to use a rod that is not really appropriate for the task, lol.
Anyway - good luck to you, my backyard creek is pretty slow now with the higher temps. Hemlock fished quite well today (Beth got 2 crappie and a smallmouth for the 1st time there) but no SH that I've seen. Bluegill were hitting pretty decent as well (as they usually do there).
Gene