Shield vs Compact in 45
I own a M&P9 FS, Shield 45, and a M&P 45 Compact and I have to agree with panamax in that my Shield 45 is a rather impressive firearm! It's more accurate than I am for sure and while the trigger is a big improvement over both the FS and Compact versions, its accuracy (at least in my hands) will improve even further with an Apex Tactical trigger job once they get a Shield 45 version released.
As for the specific comparison, the Shield and Compact (in 45 at least) are both amazing pistols and play a variety of roles for me personally. I use both for EDC depending on the situation and my mood/dress.
I realize that my comparison below will be specific to the 45 models, but I believe that it can be extended generally to all of the Shields and Compacts and can confirm its validity at least in my experience having also shot Shields and Compacts in 9/40.
There is definitely some overlap between the two, so here goes.
M&P 45 Compact - The M&P 45c is almost the perfect all-around pistol for me. If you're going to get ONE GUN to rule them all, then this is it... In one word: Versatile.
Concealment/Comfort - 4/5
Performance - 5/5
Capacity - 5/5
Aftermarket - 5/5
Weight - 4/5
TOTAL - 23
1. Concealment/Comfort - It has the added barrel length and grip feel of a full-size, but with a grip height of a Compact that makes it easy to conceal IWB with an untucked shirt and properly-sized pants. Also, the backstraps are interchangeable, which allows you to fine tune the grip feel.
It's slide length/thickness (not grip height) makes it more challenging to conceal comfortably as compared to the Shield. That said, it's by no means difficult or painful...it just requires some adjustment in your approach, which is common theme for all concealment situations.
2. Performance - It is very accurate and reliable and mine will eat anything you feed it with the added benefit of a slightly longer barrel (4" compared to 3.3") and sight radius as compared to the Shield. Not that this is needed, as most people's frame of reference is the LuckyGunner ballistics testing, which was shot from a Kahr CW45 with a 3.6" barrel with great terminal ballistics on most popular rounds, but it helps...
3. Capacity - It's capacity options are extensive. It's baseline 8+1 is great for concealment and the pinky rest helps with purchase on the grip for me personally.
It can also take full-sized magazines in 10- and 14-round capacities, which can then be further modified with the various aftermarket base pad extensions to carry even more. This makes it awesome for both home-defense and concealed carry as well as range time fun.
In home defense, putting a 10- or 14-round mag in it gives you more than enough to end the conflict, get you to safety, or get you to a shotgun

and in concealment, I can comfortably carry two 10-round mags as reloads, which puts me at 29 rounds in total.
Yes, I understand the likelihood of using this quantity is low, but in the very least, carrying one mag gives me the ability to potentially clear a malfunction and keep shooting for another 10 rounds (or 14 if you so choose). So, with only one spare mag on hand, I'm at 19 or 23 total in concealment.
4. Aftermarket - It can benefit from a majority of the available FS aftermarket mods if you so choose such as trigger kits, lights, etc that are known to fit the FS models in 9, 40, and 45. Also, it will fit in pretty much any holster that a FS M&P 9/40 will fit because it's slide length/width are the same.
5. Weight - Fully loaded, it is a tad heavy and that can tend to weigh on you for EDC depending on how you carry and in what situations. This is a very minor con in my experience, but worth noting. The key for me is balance, which I do not believe is compromised.
Shield 45 - The Shield 45 is almost the perfect concealed carry pistol for me. If you're going for pure concealability and nothing else, then this is it.
Concealment/Comfort - 6/5
Performance - 5/5
Capacity - 3/5
Aftermarket - 4/5
Weight - 5/5
TOTAL - 23
1. Concealment/Comfort - The overall thickness of the Shield makes it literally effortless to IWB conceal in any of the standard clothing situations in which I find myself. It's amazing what difference less than a quarter of an inch of thickness will do for concealment and comfort.
2. Performance - Like the 45c, this thing is just dead reliable...I've put over 1000 rounds of ball and JHP ammo through it across 9 different brands and it's never even shown signs of an issue. It's accuracy is well in excess of what I expected or have ever seen in a sub-compact pistol including the Shield 9 and Shield 40 (my personal experience at least).
3. Capacity - For the Shield 45 specifically, you're limited to 6+1 or 7+1 because you can't use other M&P mags, so your capacity options are limited. I personally carry the Shield 45 with the extended 7+1 mag in my IWB holster and two additional 7-round mags on my belt and forget its all there most of the time, so that still gives me 22 rounds in smaller chunks.
As a comparison back above to the 45c, if I chose to only carry one reload, then I'm at 15 rounds total in concealment. For home defense, its capacity doesn't concern me much, but it is definitely lower than a fully-loaded 45c with FS magazines.
4. Aftermarket - There isn't nearly as much of an aftermarket for the Shield 45 as there is for the Compact...right now at least. Obviously, it's not been out as long as the Shield 9/40's, so I think this is really more of a transient than anything...
5. Weight - The Shield 45 is definitely lighter than the Compact, but not so much so that it makes a huge difference in concealment or comfort. I personally don't put a lot of stock in the weight being a critical parameter for me personally, but everyone is different.
Look at that! They tied 23 to 23 with a 6 out of 5 on the Shield's concealability/comfort rating! LOL Yes, it's subjective...I know.
Sorry for the long-winded post, but I'm hoping it will be helpful to someone. Its about as close to what I would have wanted to read when I was trying to make decisions and never found it in this form, so I just had to pull the trigger (pun intended) and buy them both!
Cheers,
- J