Maybe it's not the most ecologically sound choice, but felt is the only material I trust in most of the rivers I fish. Glacial rivers are fine for rubber soles (even without studs in some cases), but freestones and tailwaters call for felt. I have found studs do not always improve felt; indeed, they sometimes become a slipping hazard on big, slippery rocks (or ice, but I guess not much is great on ice). I'm sure the aluminum bars improve grip, but I think they would add more weight than I like, and as others have mentioned, they are loud.
I think the only reason to have anything besides felt (where I fish; I don't deal with much snow) is to avoid running afoul of local regulations. If I am allowed, I'm generally wearing felt. I've noticed you don't hear much about whirling disease and the like these days, so I also think some of the concerns around felt spreading parasites and disease may have been somewhat overblown (at least I hope so). Still, I take steps to prevent spreading stuff between streams (rinsing and drying my boots after each outing, for example).