I've found that the biggest thing when it comes to the Turkish shotguns is to pick a reputable dealer that will stand behind their customers. They're budget guns that for the most part function well, but there will be some issues. Like others have said, parts aren't readily available from places like brownells or cabelas like they are for the Mossberg or Remington guns, so the dealer needs to have spares or parts for repairs and warranty work.
In terms of brands, I've heard that there's basically only a few real factories, but they'll print whatever brand logo you want on it, so many of the different brands were probably made in the same place by the same people.
Most stocks seem to fit across the brands for similar styles. Buttstocks seem to be pretty well universal for all Turkish guns, forestocks would probably vary a bit more.
Personally I've had very good luck with any of the shotguns Martin has brought in at Corwin Arms, I've used several hatsan without issue, and a couple of other odds and ends as well. My 5 stand gun right now is one of the original Warrior semis from corwin. Nothing special about it, but it fits me well and I tend to hit more clays, so until it wears out or I get something that works better for me, i'll probably stick with it.
For me it comes down to intended use. As an inexpensive shotgun that I don't mind bumping through the woods hunting, getting wet shooting at the odd duck and a few rounds of clays a year, it fits that use perfectly. I don't expect it to last hundreds of thousands of rounds like a high end skeet or trap gun, but I also don't shoot enough rounds in a year for it to really matter.
