With everything else being equal (shot payload, same type of wad, comparable powder charge...etc) the larger bore will throw a more uniform pattern. However, the difference may be negligible, so it will probably come down to personal preference in the guns themselves. Whichever gun fits you better, and you are more comfortable with, will probably be the gun you will be more successful with.
I can't remember where the information on these pattern difference is documented (although I know I have read about it before), just going on my own personal experimentation with different gauge guns over the years. I've seen dramatic differences between 10 and 12 gauges guns, with equal payloads of larger (4 and up) shot. The pattern differences between small shot sizes, and smaller payloads are not as pronounced, hence my recommendation of picking the gun that you are more comfortable with. Or, if you are able to, do some experimentation yourself with the exact loads you want to shoot.
