I have two sons who have very similar WISC-IV profiles except in the area of working memory. My younger son's WMI is about 40 points higher than the older son's. Their PSI scores are the same and quite a bit below average.

I'm sure there are other differences (one being the older one has dyslexia and the younger one doesn't), but the difference in their ability to learn is like night and day. The younger one is very much more obviously gifted.