Ok, I got it.
pHash can't recognize rotation and critical movement as same thing.
In case of data space, pHash was dramatically good for using. It is very small size: one image to one hash. SIFT, however, need 128 bytes to get feature point. And there are many feature points in one image.
Eventually, SIFT can identify similar image well than pHash. But more and more size was needed.
In speed bench, I can't test yet. But I think, pHash was faster than SIFT because SIFT have to operate for many features on one images.
If you have another answers for above question, tell me please.