This seems to be a fast growing handgun market segment. My hazy memory returns recollections of the excellent Walther PPS as one of the first. I believe that Sig Sauer followed in suit with the P238 1911 based pistols. The Sigs are all the same gun under the skin but following SigUSA's philosophy of "build cheap, slather on cosmetics, sell dear," I would not recommend a new Sig. Neither would the United States Federal Air Marshalls (FAMs), having grounded all of their shiny new .357 Sig chambered Sig P250s to the intense relief of the poor marshalls who were issued the unreliable pistols.
Kimber released the Solo this year. Not gonna touch it. It might be fine for those of the "carry lots, shoot little" crowd but I like to shoot my pistols. Maybe if someone shows me one that did 500-1000k rounds without malfunctions, preferably without cleaning, I'd be interested.
The Walther is my pick. I've owned one and I sold it to finance a S&W M&P purchase. I hope to purchase one again sometime this year. The way I describe it to friends seeking impressions of it is:
Imagine a Glock 26 cut in half with a better trigger. A very flat pistol, good for concealment. Needs break in but runs well after a few hundred rounds. In other words, runs best with hotter 9mm ammo during the first few hundred rounds.
The little PPS has differently sized backstraps for adjustable fit to the shooter. When you remove the backstrap, the weapon is disabled from firing. On disassembly, the internals remind one of a Glock. Looking over the internals, it was readily apparent to me that the 25 cent Glock trigger job is relevant here and Voila!, it worked perfectly.
The PPS only comes with one six round magazines and magazines are expensive, roughly $40 per mag. The good news that these mags are available with and without pinky extensions (for your bottom finger to rest one when gripping the pistol) in six, seven, and eight round mags.
Walther P99 night sights do fit the PPS. The paddle magazine release located on the trigger guard is wonderful once you get used to it. The de rigueur accessory rail is there. If you attach a light to your pistol, please remember that is not for say, finding your keys or friends in the dark. LEOs have accidentally shot suspects because they were using their weapons mounted light as a flashlight with their finger on the trigger. Not a good practice. The end of the striker protrudes from the rear of the slide when the weapon is ready to fire and it's both visually apparent (painted red) and felt by touch.
Recoil is a bit more snappy (slightly) than the Glock 26. My experience is only with the 9mm PPS. I am sure the .40 version would have very snappy recoil.
I like the PPS a lot. I don't generally fit the weapon to my mode of dress but rather vice versa. This is the one you should consider if you must have a smaller, more easily concealed pistol in a real caliber. I don't like revolvers and prefer the more simple (far less moving parts), more shootable, and easily reloaded automatics. Its dual recoil spring dampens recoil enough to make an actually shootable pocket sized pistol. Price range is from the mid $500's all the way up to $700-ish. I wouldn't pay more than $600 for one.
Poor pics by me of size compared to a Gen3 Glock 19 and groupings at 25'. The Walther is actually much smaller than the pics appear to show.