I don't think I'm going to be able to answer this with any specificity, as it's been a decade since I watched a lot of Xena and Farscape vids. I will say the differences are not (to me) huge, and they are what you'd expect from any kind of parallel evolution: same destination, different journeys to get there, if that makes any kind of sense.

I'd never claim that the Buffy vidders were deriving what they knew from Star Trek vids; the Buffy vidders I knew were themselves from the Nummy Treat list, another kind of parallel evolution. But I'd say that branch really merged with the vidders who came to Escapade and later Vividcon, whereas the Xena and Farscape vidders remained separate -- except a few people like LithiumDoll and Sebaceanbabe. So while the Buffy aesthetic influenced the traditional one, I haven't seen that kind of cross-pollination happen with FS and Xena vidders.