I like the format and so I investigated XD-S and Kahr P45/CW45. Together wth the Shield, these three are the only slim .45 on the market outside of 1911 compacts (and Boberg XR45-S, obviously).
The XD-S has recoil amplified because of the shape of its grip. I like its features and I would love to have one despite its weight, but it hurts to shoot, so it's not fun at all. Note that many people shoot XD-S fine and it's all down to your compatibility with it.
The Kahrs have the most ergonomic grips, although it does not look like it in pictures. The design looks blocky and straight, but it's the easiest to shoot. The triggers have long travel, which I actually think is an advantage for safety reasons. However, my P45 required too much tinkering to make it run properly, and even so it cannot be trusted completely.
As an aside, Kahr also makes a smaller series, PM45/CM45. Neither S&W nor Springfield ship a version that's comparable to that pocket subcompact. It's basically PKO45 sized, just thicker.
Shield's grip is thinner than Kahr's, and it feels more like XD-S. However, S&W made every effort to shape it in a conforming fashion, so it's not much worse than Kahr. It may be better for many people. The gun is fully reliable out of the box. The only downside for me is, the magazine release is not adequately protected with overmolding, so I tend to drop magazines accidentally. Unfortunately, I do not expect S&W ever to come with a different mold line. I suppose one could create a barrier around that button from JB Weld.
Because Kahr refused to supply flush magazines for their .45 ACP line (although they did for 9mm & .40), and because Shield uses a semi-staggered magazine, the grip of a Shield when loaded has exactly the same size as CM45, but capacity is 1 round larger (6 versus 5). Of course if you're really concerned about that, you should rock Springfield XD Mod.2, Glock 30S, or SiG P320. But otherwise hey, a free round. It's like MagGuts +1 from the factory on the Shield.
