I realize this is an old post, I just found it looking for rails.
The SIG rails sort of clip into the front end of my pistol with some minor pounding and pin alignment. Even with the tight fit, it isn't enough to retain zero with an optic or a laser mounted to the rail (you can move them around with a vertical fore grip, or just rough handling). The Troy rail is very solid, and should be since it clamps to the rail on the receiver, I don't have any experience with the Sampson, but it appear to be the same, just a different flavor.
The draw back with the after market rails is that the rail, and thus sights, are now higher from your cheek weld. If you haven't spent money on BUIS yet, Troy now has short sights to solve that problem. (my wife has this problem with her AR rifle, and I have been looking for something, right now the SIG red dot on her rifle works the best).
I don't think its a one or the other decision as far as SIG or other. The added sight height can be a problem for some. I SBRed my pistol and can fit my Aimpoint on the receiver rail, and don't plan on a laser and its a perfect cheek weld where it is at with AR height flip up sights(with the SIG sights, I would have to lower the stock). I am considering putting the short Troy sights on my AR so I can really put my face on the stock instead of kind of kissing it with my cheek, which is one of the reasons why I am beginning to prefer the SIG over the AR, you can get "into it" instead of just behind it.