With good auto completion, the user should never even have to press the compile button or hit a compiler error. (Slight exaggeration) This means the user might

With good auto completion, the user should never even have to press the compile button or hit a compiler error. (Slight exaggeration) This means the user might have struggled a long time with the code before even hitting the compile button. If you only collect statistics from compilation you will miss all this pre-struggle.