RE: 4120 vs 4130: Your project experience
...and those 10 different answers would probably all be correct! That's the beauty, and the bane, of electrics. You've got so many choices and so many "right" answers, that it can just overwhelm you. Heck, just within the 41XX series of motors, you have two, maybe three, that would be suitable to fly a generic .60-size sport plane on 20 cells, along with at least two or three possible props for each motor! Imagine if we were talking about Hacker or Mega motors... With a gearbox in the mix, you're talking about hundreds of viable combinations. [X(]
To help make your decision easier in these situations, go for the largest propeller that will fit on the plane without creating ground clearance issues. Heck, extend the landing gear if you're not particular.