This thread is more interesting that I would have guessed. I thought standard practice was to teach both. That's what we did when I was a student pilot. Crabbing was emphasized as the better technique for managing larger cross winds (and we students figured it out, just fine).

It's obvious to any pilot proficient with both slips and crabbing approaches that the cross wind limits of the crabbing approach are vastly higher than what you can manage with slipping alone. About 50%, I'd reckon.

see also: Peter Schiff, The Proficient Pilot.

best,
Evan Ludeman / T8