I owned a SR1911, very nice pistol. For the money that is the best bang for the buck, no pun intended.
It has every option I like seeing on a 1911; beavertail safety, combat hammer & trigger, nice grips, SS finish and Novak sights. It also does not have things I don't like on a 1911; front slide serrations and a rail. I'm sure there is a place for these features but just not for me. It had a very nice trigger right out of the box, shot straight and never gave any problems. The only reason I parted with it was the fact that I made a nice little profit on it, even after having it for almost a year and shooting it quite a bit. I have to admit, it still looked new and the guy that bought it was tickled to get it. And it's AMERICAN made!!
As to my S&W 1911, it's a 9mm Pro Series and is top notch. I have to admit I much prefer a 9mm over a .45 for several reasons. I realize the 1911 .45 purists are cringing right now and I respect their opinion but for me the 9mm is great. Less recoil, much cheaper range ammo and a more than sufficient self defense ammo. However, back to the question at hand. My S&W is a fantastic pistol and again has all of the same features of a Ruger, however, it is actually worked on at the S&W custom shop so it's a bit more pricey than the Ruger. I can say the tolerances on the S&W are tighter, little to no rattle and shoots exactly where I aim it. It is slightly heavier than the Ruger but that just helps to manage the recoil even that much more. And again....AMERICAN made!!
As for the Sig I can't comment on it, I have never seen one. Like myself, I'm sure most of the reviews you have read about them are positive. The Sig Stainless 1911 looks just like a Ruger and S&W. Depending on the model of pistol Sig is manufactured in both Germany and America.
Purchase price is as follows starting with the cheapest:
Ruger - Sig - S&W E series - S&W Pro Series
I still say for the price the Ruger is hard to beat, why spend an additional $200 - $400 when you don't have to. This of course is taking into consideration you have decided on a .45; if a 9mm is an option you have a whole other set of pistols to look at.
Hope that helps. Good Luck.