Good question. I can only share my personal experience; I've seen 5, but only 2 seemed to understand my pain and gave me exercises tailored to my needs (using elastic bands, aqua exercises, stretching, etc.). The standard for back pain seems to be core strengthening. I found aquatic exercises most helpful (and least painful) for that.

The best ones I've seen were both athletes who succumbed to back injuries. But there must be good PTs who learned by the book too... I hope.