Same cartridge but when it comes to design, there are significant differences. 1911s are hammer fired whereas the SR45 is striker fired for one. Which is the better gun is a can of worms just begging to be opened.
We have several SR guns and enjoy shooting them all. As to the SR45, wife hasn't found one yet but one will be in the safe (and on the range) soon enough. As to our 1911, well ... it's a 1911 and that says a lot on many fronts to me.
Assuming you develop your skills and practice often enough to maintain them at a high level, either gun will serve you well for defensive purposes.