Several years ago I asked my programming teacher about a rumour  I heard about other teacher being better than her teaching programming.

She told me that the other teacher was good, maybe even great, sometimes the students from the other teacher got better grades than her students on the exam, but she never went to a class given by the other teacher to actually check if she explained better or not than her; but more important the other teacher had a major flaw that couldn’t be repaired in any way, I asked what was it, and she told me that matter it fact all the other teacher had the same flaw: they weren’t her.

That was a long time ago, even before I became a teacher but everytime a student of mine asked me if another teacher is better than me, I just reply this, (s)he might be good but it has a mayor flaw, it ain’t me