It's always better to go with larger IMO, but if it gets too large, your chinny may have trouble turning it. Are you looking at the metal ones or the plastic ones? I really wouldn't recommend the plastic because your chin may decide to chew on it and then it's just a waste of money. Also, while I haven't purchased one myself, the plastic looks very flimsy and doesn't seem like it would stand the test of time, but that's just my opinion.