Maybe it's because not that many people have the Evolution engine.
The posts are in the hundreds for the O.S. Most good but some bad.
The evolution has only a few posts that I can find and they are all good.
I have a .47 GMS not very reliable. Very good top end. But it stalls out a lot. It only wants to work on very (extremely lean setting) 2-3 clicks into the rich and it works like crap. This thing has been a lot silicone on it to block possible leaks. I don't believe I should need to drill this or modify that to make it run well. Shouldn't it do that without all the mods. Well enough about that I've pretty much given up on the GMS. I want to be a flyer not an airplane mechanic. I may stick this thing in another plane, but not my trainer

The evolution sounds good, but the manufacturer wants to sell his product. The claim is that it is as good as anything else out there.
I like the rear carb adjustment. (layer of skin knucles gone) from tuning the GMS.
That's why I'm either contemplating the OS AX46 or the Evolution 46NT.
I'd like to hear from people that have the Evo.