Try some info on this recent thread....CLICK HEREWe have talked size a good bit before, but it does make a difference in both volume and balance. Woods also make a difference and the combination can be quite different. An M (or 0000) has great balance but a dreadnought loses some in the treble. However, a mahogany D is less muddled that a rosewood D.
Combine all of this with the "fit" of the guitar to you and your general feelings. Best bet is to play a lot of them and refuse to get hung up on brands, woods, or anything else during the initial shopping phase. Don't forget to have someone of a similar style play a bit for you with your back turned and see what you think. Do the comparisons and you can't go wrong.
Spaw
Spaw