Smaller eggs of the same breed tend to hatch a little earlier than larger eggs of the same breed. That I am convinced of. I do not know if bantam eggs tend to hatch earlier than regular eggs. I have no experience with bantam chickens.
What I mean by tend to hatch earlier is that if you have a lot of eggs, you'll notice a difference. But if you only look at a very few eggs, it does not always work. For averages to mean anything, you have to have enough samples.