Yeah ... if I were going to pick a tempo for all drummers to set a goal for, it would be 40 bpm. In fact, quite a few legendary drum instructions recommend 40 bpm as a starting tempo when working on various coordination exercises, sticking patterns, etc.

I agree ... playing slow is tough; playing soft and slow is even harder.

My belief is that if you can't play something slow, with control, then your faster tempo is probably sloppy and out-of-control; you just think you are playing it well.