Steve, I have Shield's in 9mm and .40.
I had a .45 Shield briefly, but was not all gagga over it like most.
The .40 I bought first, and it is the Performance Center model that has two small ports near the muzzle, and a much better trigger than the standard Shield models.
The ports are large enough to noticeably tame recoil, but not so large as to cause problems with excess flash, noise, etc.
If you can find a PC model in 9mm, it would be worth the extra coin.
The .45 I was not crazy about, it is longer in the slide/barrel and longer in the grip than the 9mm or .40 models. Not by much, but enough that it seemed more like a full size gun than the smaller 9mm and .40. The .45 is larger enough that many holsters for the .40 and 9mm won't fit the .45.
So I ended up trading the .45 for a 9mm Shield that I plan to give to my daughter.
All three Shield's are very accurate though, surprising for such a small pistol.
Only FTF's I had were a few with the .40, but that was probably a combination of not being broke in yet, and the ammo I was using, those yellow box Remington-UMCJ's that have such a flat tip on them.
The 9mm should be the most reliable chambering due to the slightly tapered case and such a rounded profile bullet in most loadings.
I put a Streamlight TRL-6 on the .40 and will get one for the 9 before I give it to my daughter.
Pretty cool that they can make such a tiny 100 lumen light and a laser and sell it for less than $100. There are several holster makers that make a holster to fit a TRL-6 equipped Shield.
One other thing for the Shield's that I like is the Pierce magazine extension.
No +1 capacity, but they give a place for your pinky when using the shorter magazine that you get with the Shield. Now that I have the Pierce extensions, I bought several more 6 round magazines ( 7 round in 9mm ), and prefer them over the longer magazine with the goofy sliding spacer.
I had planned to include some pics and targets of the 9mm, but my internet connection is really slow this morning.
