I have the MTAC, so similar but not exactly the same as the Spartan you are looking at. I believe the difference is the addition of a piece of leather on the back of the MTAC to cover the rivets on the back so they aren't directly on your skin. Anyway, mine was ordered for a Colt Defender. I also have the Cross Breed Supertuck. Both are nice holsters. I had the Crossbreed first for a PX4sc. The reason I went with the MTAC was simply becuase I decided that way, rather than another $80+ holster if I wanted one for another gun, I could just get the $30 Kydex and replace it on the leather I have on the MTAC. Other than that one option on the MTAC (and Spartan I believe), they are both great holsters. The Cross Breed seems to be "better" leather. That may not be fair though since I paid for the horsehide on the Cross Breed. The belt clips on the cross breed are steel and look nice. However, being steel the edges are sharper and it did scuff up my seats in the truck. The MTAC has plastic hooks, which I was initially afraid might break. While they tell you to be careful pulling on them, I have put them through there paces with no signs of problems.
In short, I think you will be happy with either. For me, the MTAC won out becuase of the replaceable kydex for different guns. That said, I still like my Cross Breed, though I sold the PX4sc. It still works for my full size PX4.