If you can size your shot to give proper windage and can handle the heavier gun, I would go for 3". As they say, "size matters."
Obviously it will cost more to make and more to operate. but you know your financial situation better than I do.
With either size, I would expect it would be easier to find shot on the quarter or whole inch than shot sufficiently smaller to give good windage without excess windage if the bore were on the quarter or whole inch, so I would overbore the barrel to give windage in that case because it wouldn't require special sizes of shot.
