What you are saying is all true.
To say that McKenzie has done nothing for the Bills this season is foolish. The problem is that we all expected a lot of good things from McKenzie during this season. Just as we did with Davis.
McKenzie has just been too inconsistent, and while Beasley has played very little, there's a feeling that Beasley can become a more stable contributor.
It might be wishful thinking, but we have seen Beasly come up big for us before and he could very well do so again.