Regarding ammo, (specifically 9mm), for compacts, snubbies, is there that big a difference between standard, +P, is +P wasted on a short barrel gun, is 'short barrel' the best way to go. I spent a little time on the Speer site, the differences aren't that big, about 10%, (maybe 10% IS a big difference, IDK), interested in the what the experts think.

Too many variables from gun-to-gun to say for sure. Bullet placement means more than any certain number on paper. Plus P ammo will give the maximum velocity/energy of any load, where "short barrel" loads are designed to expand at the lower velocity from short barrels. With revolvers it's more of POA/POI question, but with autos the relieability is more of a factor to consider. Look at it like this, no one ever survived a gunfight wishing they had a less powerful gun.

There is usually quite a big difference between standard pressure and +P loads, in any caliber. Shoot them both and the difference is readily apparent. Short barrel loads MIGHT be best, depending on the gun. These are usually +P and more powerful than standard pressure loads. I haven't made a direct comparison in 9mm yet, but I know that in my .38 LCR, all the +P loads are MUCH stouter than the standard pressure. And in my gun, the 125 +P Golden Saber is noticeably more accurate than other rounds, whether +P or not, including my own handloads and the Speer +P 135 Gold Dot Hollow Point. So that's what I carry. Test as many different rounds as you can and get the round that works best, for you, in your gun.

Yeah, it's amazing the difference in accuracy between different ammo, when I first took my Sigma to the range, I was using reloads I bought online, then through a clip of CorBon +P HP in and they where much more accurate, loved the accuracy, didn't love the cost so much.