Crab.
For people aspiring to a career Crab is what you will need later in your career and trust me a B737 is just the same as a PA28 in that respect.
Crab is generally easier and safer in my opinion. The issue of stall leading to spin with wing down is very valid.
Crab is how the large FTO's teach.
With good students I like to teach both techniques and see which they are best at. With not so able students I stick to crab.
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