Don't know the laws in your state OR how old you are, so you'll have to contact your DNR representative to get you that info. Call them, they are very helpful I've found.

I owned a 20g as one of my first guns. Loved it. Hate that I sold it & have been trying to buy another one ever since (20+ years). It has enough power to do any kind of hunting, and it is also lighter in the kick & lighter in the weight SO it is a pleasure to carry for long days of hunting (this is key).

20g shells are cheaper than 28g also, other wise, I'd say the 28g.
The 28 is the best small game gun to carry all day. Soft kick, super light, super accurate, just a pleasure. Not a canon LIKE the 12 gauge. Love the 12, but it is heavy in carry weight and kick.

This is why we buy more than one gun!

20g, I'll stick with that choice. Good enough to get you going in all directions...