Being a Plusle fan seems to be like being a Charizard fan-- it's cooler to not be one and go for the underdogs. Which I usually do, but in this case, with stats like theirs, they're underdogs anyways.
I'd like to say I like Minun equally, though Plusle's got a definite edge on me, what with being in Colosseum, and back when I used to draw a lot of Pokemon comics, Minun was kidnapped or something for like three issues, allowing a lot of character development for the very quirky, slightly eccentric, and very happy go lucky Plusle, that Minun was never able to catch up to, just being the sensible one of the two, trying to keep Plusle in check. That's probably how I see them now, even if unconciously, and with a party pooper personality like Minun in my mind, I guess I would prefer Plusle.