Some previous customer reviews mentioned that the gloves seemed too tight / small.
A Revzilla video review mentioned that the gloves might be slightly large.
So I balanced those opinions and stayed with my normal size (Medium). (For reference, I have relatively big palms and short fingers and usually wear medium in all sorts of gloves.)
I should have listened to the customer reviews. I'm working on stretching them out, but these are pretty small and tight.