Shield is a solid choice. I had one, and don't remember any hiccups. Solid performer, decent trigger out-of-box, and nice slim profile. The gun that beats it? XDS. Way more fun to shoot. I'm actually more accurate and quicker to get back on target with it in .45 than I was with the Shield in 9mm(had a somewhat snappy recoil). Also 100% reliable. Better trigger imo. Profile/proportions nearly identical.
Downside you lose 2 rounds if going with the .45, but I believe the 9mm XDS has the same capacity as the Shield offering. Other downside, price.
I sold the Shield before obtaining the XDS, but I'd choose the Springfield over the S&W any day if money isn't an object...obviously, as I kept the XDS and don't feel much remorse over the lost Shield. IMO, just a better handgun all around, but it should be since it cost $125+ more. FWIW OTD prices compared, when I picked up my Shield I got it for $390, the XDS for $520 (then I went and got the bitone for $565 as needed to break up the monotony of the all-black club). I have no problem putting that extra money into the Springfield, but for those that are looking for the best value the S&W is the no-brainer as it's still a fine firearm.