They're all good guns, but they're three different animals.
+1
Very different animals. Kahr K9/K40 are very small, very slim guns. Easy to carry concealed. The K40 recoil is stiff. The K9 is not. Kahr's have a very long, smooth trigger pull, with a relatively long reset. They are accurate, but take some work to shoot quickly and accurately. These are single stack guns. They have a nice low bore axis, so they don't have much muzzle rise.
The 229 is a much, much larger gun, with a double stack magazine, and a DA/SA. The DA trigger is ok, the SA trigger is pretty good. It will take a fair bit of work to be able to quickly and accurately fire the first DA shot and the second SA shot. Sigs are generally pretty accurate.
The 239 is a single stack gun, significantly smaller than the 229, but still much bigger than the K9/K40. I find the 239 to feel top-heavy in your hands. It has the same DA/SA trigger like the 229. I find the 239 to have a lot of muzzle rise, probably due to the high bore axis. It is a single stack gun, with a capacity similar to the K9/K40, but still significantly larger.
You really should try to shoot them if you can, because they are very different guns.