I don't have any of those guns, but I have the SIG P250 Compact in .45. The P250 has a DAO trigger and is hammer fired and P320 is striker fired but they are otherwise practically the same gun. It is a little larger than many people prefer for carry, but it is small and light enough to do so. I find mine pretty comfortable when it accompanies me to VA or another state where I can carry on my UT non-res permit. The P320 Carry is a tad bigger (compact slide, full size grip module/frame). My P250 is a joy at the range- comfortable to shoot, accurate and reliable. I'm pretty sure the subcompacts are your only option if you don't want the rail (I don't use mine and it doesn't get in the way). As for looks, it is a modular, polymer CCW pistol, it won't win any beauty contests either way so I'd suggest that you not let the rail get in your way if you otherwise want the gun.
As for the P224, if you want one you may want to buy it now. The website doesn't show any P224 models on their product list, but has several on their list of discontinued models. My favorite local FFL, one that usually doesn't spread rumors and confirms their info before telling people, tells me it has been discontinued. So, if you want one, now may be the time. It is based upon the P229 so parts shouldn't be a problem, there are holsters out there for the gun, and you can always use P229 mags in the gun as well. It is a little heavy compared to the P250/P320 Subcompact, but otherwise is sized similarly, and if you are used to carrying the P228 and P229 the weight should be fine for you and it will be a good carry gun.