Clifford Ray is the best big man coach in the league.
McHale would be a downgrade.
I think you're incorrect on both counts.
Clifford is definitely very good at what he does. Glad to have him on the staff and I wouldn't want to dump him just to get Mchale. Having said that, I think it's a leap of faith you're making to call him the best in the league. Do I have a suggestion for who's better? No, but I don't follow the league's "big man" coaches, hence my questioning his being rated the best.
Would Mchale be a downgrade? Not sure how. Comparing the two in their careers, Mchale was superior. He had no peers in the post for offensive moves and he was a top-notch defender. Hard to understand how you would rate him a downgrade without some solid basis for that reasoning. If you have some good rationale for your opinion, please share.