Over my last 28 rides on the road bike, my overall average cadence was 83, so I guess that puts me into the spinner camp. As an older rider, a higher cadence in a lighter (i.e. easier) gear is probably better for me. By all accounts, it's easier on the knees.
I notice something odd, though. Even when I work at riding on the big ring, which naturally slows my cadence, I want to increase my cadence because the lower cadence makes me feel like I'm slower -- even when my speedometer tells me otherwise!
Re: which type of muscle fiber is getting used, I was surprised to learn that high-cadence, low-gear spinning brings SLOW-twitch fibers into play, while low-cadence, high-gear riding uses FAST-twitch fibers. To me that sounded counter-intuitive. The explanation was that low cadence in a high gear means the muscles have to make harder, faster contractions. The more I think about that, the more sense it makes. In fact, once I started paying attention to how my legs felt in low cadence and high gear, I could sense it as I rode.
I'm working at increasing my endurance for riding the big ring, and in fact I can now push it at a cadence in the 70s, whereas six months ago 60-something rpm was the best I could manage. Progress!