I have caught fish on both baits but there are some differences between the two. The Spro dive quicker, pull harder and have a narrower body (litte john) and flatter sides than say a 3X or 4X SK, the result is a tighter and faster wobble. They both work, sometimes one will when the other wont. I think the quality of the Spro is slightly better than the SK, but that is just my opinion.