I always struggled with the corner shots because I have less of a spacial reference with the side of the backboard facing me. Shooting from the top of the key should be much easier, no? I always had the most success with the 45 degree angle one, right between the key and the corner. Maybe that’s just me though.
for casual players the corner may indeed be the hardest one for what you say. for nba players the shot is almost completely mechanic, they rely on muscle memory from repeating the shot thousands of times and has nothing or very little to do with spacial reference. being the closest shot makes it the easiest in this situation because it requires less force and precision which are things that tipically dwindle in a game due to fatigue/pressure/etc.