I like gloves because I can be a bit more nimble with the fingers, but I get the distinct feeling that mittens are better because the body heat form fingers touching each other keeps them warmer. Gloves usually only keep my palms warm, but fingertips are floating out in the cold abyss... Still, I'd feel a little silly with mittens. Although, the hybrid ones seem like a good compromise (finger cutoffs with a mitten flap).
Gloves, unless is a "specialty" mitten. There are a couple pairs of her horse riding mittens and my marksmanship mittens around here (think free thumb, 3 fingers together, and a 4th free, pinky free for riding, trigger finger free for marksmanship.)
I like glovelets- they are gloves that only cover half of your fingers, but they come with a mittencap flap that keeps your fingers warm too. that way I can still use my fingers and keep them warm when I want to