I think there's an optimal size which is related to the size of your fingers, and thickness of coin comes into it as well.
I've got quite small hands, and very narrow fingers (with socking great windows between them because my knuckles are thicker than the bits between them) so I preferred a slightly smaller coin.
I used to put most practice in with 2p pieces (apart from when I was trying to train-the-harder-trick-to-make-the-easy-one-work when I'd use a 1p) and they suited my fingers well.
I don't like the £2 coin because it's too thick (and the texture is "all wrong" is some hard to articulate manner) and a 50p felt wrong because of the shape. I've never had my hands on a silver dollar, but I did a lot of work with the smaller half-dollars purely because they're so common in magic circles - a fact which is another source of irritation to me whenever I see a coin magician working with dollars/half-dollars in the UK.
So if a coin feels too big, or too small, try a different coin - it might just suit your fingers better.
by Little Paul, in response to this post 2016-03-08 12:20:07