First off I am not a Blade-Tech Dealer.
Asking why a place only has one brand on the shelf, you must ask the question--of wholesale cost to MSRP--read profit margin; its much higher on Uncle Mike's than it is on Blade-Tech, Sidearmor, G-Code, etc. I would also venture with the connection of Blade-Tech and Sidearmor to "official" suppliers to Gunsite they are reluctant to sell to Gunsite's competition.
The comparison is simple; look at Uncle Mike's other products and that will explain the quality of the injection molded kydex. Their nylon and fake leather lines are known for low quality and the theory of one size fits most firearms of a size but not really any of them well. The double belt loop, allows the handgun to set from the body, making concealment more difficult.
Its a case of what you want to pay and what you consider quality. When it comes to Uncle Mikes Holsters, they ain't it.
If it works for you that's all that counts. Personally I would not bet the farm or my life on Uncle Mike's. Before you bring up what all the guns-n-bullshit writers have to say, remember, Uncle Mike's spends boats loads of advertising bucks; lest we bite the hadn that feeds us.