To me it looks like the redline keeps the engine cleaner (not the plane lol). I switched from stihl to redline earlier this year. I have pictures from one of my 120's of the cylinders with aproximately 20 gallons of strictly using stihl hp. I have another 120 that was completely rebuilt (new cylinders/pistons) when I switched to redline that I have easily burned well over 20 gallons in since the switch. Next time that plane is down for maintenance I will pull the jug off and see what kind of difference there is vs the other 120 that ran stihl. Also on that note, the engine that ran stihl but wasn't rebuilt when I switched, is still blowing all kinds of junk out of the exhaust since the switch to redline....I can only assume that its cleaning the inside of the engine and once I get more time (I probably only have around 3 gallons through that one since the switch) I will pull a jug off on compare to what it looked like prior to the switch. I did however have a muffler slightly come loose on the 20+ gallon engine and while I had the muffler off to redress it, I shined light in there and looked through the plug hole and to me I could not see any carbon build up on top of the piston and from the exhaust port, from what I can see the piston looks dang near brand new.
As for any gain in performance, I haven't noticed any difference there. I'm also not a temperature nazi so I don't know if the engines running any cooler or not. As long as my plugs aren't indicating lean or as long as the cylinders aren't scorching hot or discolored and the engine is not losing power during abusive flights, I call it good. I also check my plugs quite frequently when an engine is new or has changed planes to make sure the back cylinder stays a nice dark bronze/light brown color and doesn't turn white or black. Usually the front cylinder plug is a shade darker.