I have had both, I have had the 520 sold it. It was a great knife, I later bought a 525 and that is just the smaller version of the 520. Great knife. I also have a BM 550 Mini Grip, sheepfoot blade. It is almost the same size as the 525 just a little less weight. It is a great knife. All three are Mel Pardue designs. The 520 and the 525 have thumb studs and the 550 has the oval hole. You get a great knife with any of the three but the Grips cost less and work just as well. Almost the same blade styles. I almost think if I were doing it again I would pick one of the Grip models. There is the Ritter models with S30V and the ones from Cabelas with the D2 steel and the the standard 154 models from BM. There are still some 440C models out there in the pipeline also. Have fun.