My "single stacks" side by side. XDS .45 and my Shield in 9 mm. Both are great EDC's. Recently had Tru Glo TFO's installed on the XDS and will soon have them on the Shield.
The ergonomics of the gun, and how it feels while shooting! The two guns are very similar measurement wise, and I've got talon grips on both guns but the xds in my hands is a better fit!
It is a blast to shoot. Still take my XDM any day though. I almost bought this RI but decided on xd, them brother went an bought this one.
Really. I have three of them and have never had problem one with any of them. Quality is good, fit and finish is good, and a warranty second to none.