The following is based on my experiences. I have no recorded data to corroborate my opinions.

All of the props you mention are popular on 40 size profiles with 46 - 55 two stroke engines. All work well, and I do not think one is better than the other. The trick is to match the prop to your engine and flying style.

Out of the three I think the 11.5x4 is the easiest to turn so it gets praise for fast spool up. The 12.25x3.75 takes a little more engine, but provides more thrust. The 12.25x3.75 is the prop I use on my Webra 50 & 55, and Irvine 53 engines. I have not played with the 12x4 as much as the other two, but I think it falls between the other two when it comes to how powerful of an engine it takes to turn it like we need for 3D.

Since the blades on the 12x4 are not as wide as the 12.25x3.75 I would guess you would see a few more RPM with the 12x4. If your engine is strong enough to handle the 12.25x3.75 you might get a little more thrust. Trial and error is the only way I know to figure out which one you like the best.