Weight is a factor in this stuff too....( the gun ) ...not me (quit laughing ...)...
For a general purpose gun ...hunting in the field ( at least upland birds ), for Skeet and for Sporting Clays....regardless of gague ...I like a gun that is around 8 1/2 lbs ...and in an O/U with 30" barrels.
In some situations - I might want a gun that is a little lighter ( 1/2 lb ..to a full lb ) but not less than 7 1/2 lbs.../ but my point is....I want the gun "lively" ...but not "whippy" and not too light so I slap at targets vs giving me a smooth follow -thru ...and with enough weight ( where I might shoot 200 shells a day in sporting clays ) that it doesn't beat me up / because a lb of weight in the gun cuts down recoil between 15-20% for any given shell. The length of the barrel and the overall length is important too ...so I get a good sight plane. In general ...if I go to a really light gun ( like a Benelli semi-auto at 7.2 lbs ....then I want a 30" barrel on it ) making it a little longer overall - than an O/U with 30" barrels ...because the longer overall gun helps me smooth it out.
Trap is a totally different game to me.....way less left to right ...or right to left barrel movement ( although there is some ) ...but I want a gun that is around 10 lbs...and in an O/U in 32" barrels.../ if I go to a single barrel gun, I want it in a 34" barrel. The extra weight - helps me keep my smooth follow thru.../ and if I go a little lighter - then I want longer.
To me - while I can shoot a 32" O/U at 10lbs on a skeet field ...it feels more like a "big ole sewer pipe" rather than a "nimble gun" in my hands. I wouldn't want to carry a 10 lb gun around all day after Quail or Pheasant either...its just too "clumsy" ...but it feels just right to me on a Trap field.
I realize I'm a little bigger than the average Buffalo...
...and my shooting buddy who is probably 6' Tall and 175 lbs ....agrees with me in concept ...but for him, his general use gun - skeet gun is about the same weight as mine ( 8 1/2 lbs ) but he likes it in 26" barrels. For Trap he goes to an O/U in 30" barrels at a little over 9 lbs...or a single barrel in a 32". So he takes a little weight off the gun and 2" off the barrels to suit him.
So this isn't an exact science...its whatever you like...