P11 and here's why.....
It covers all of your parameters. I owned one of these and it would be a formidible close-quarters self defense pistol.
No other gun of it's size has the 10+1 full 9 mm capacity.
It is completely flat and easily carried IWB or in the pocket in a squeeze.
It weighs less than 20 oz fully loaded. It is a true double-action in that if you get a "click" just squeeze the trigger again for a "bang."
It has 3-dot sights. (Tritiums are an option)
The P11 has many aftermarket options and even an enthusiasts' forum:
The kel-Tec Range or KTOG. I learned more about practical pistol maintenance from these forums than from anywhere else.
The only possible drawback is the rather l-o-n-g trigger pull. I disagree with some that say the P11 has a heavy trigger; on the contrary, I find it light and smooth, just rather long.
Accuracy is quite good from 10 yards on in. Think about it.....When are you going to be shooting at a target in self-defense from beyond 10 yards? Possibly never.
Kel-Tecs are warrantied for life. I've owned the P11, P32, and P3AT and you will appreciate the simplicity of maintenance on their products.
Kel-Tec backs their guns with excellent customer service.
Some say Kel-Tecs have reliability problems. You may hear of more but there are not many manufacturers that sell guns in mass quantities like Kel-Tec so I think it is a matter of ratios.
Good luck on your first purchase.