For me, as far as "backup guns" or "pocket guns" go it is always a decision between my:
KelTec P-11 9mm with 12+1 rounds of +p 9mm,
or, my
S&W Titanium-Airweight J-Frame revolver (model 342 I believe it is) with 5 rounds of +p .38 special and a Bianchi speed strip with 6 more rounds.
They both have belt/clothing clips on them. The KelTec has the factory belt clip on it and the S&W Ti-Airweight snubbie has the "Clipdraw" on it. I usually clip them in my elastic waistband when I have sweat pants on and such, or throw them in a pocket, always in the same general location on my person.
The Kel Tec 9mm is a hair heavier than the titanium revolver, but with much more firepower. With the polymer frame, it does stay in the pocket or waistband very well because the weight is high and "forward" due to the heavier metal slide and barrel. I do have problems with rust. I use Tuff Cloth, but wish I had the stainless version.
The S&W Ti-Airweight is lighter, albeit much less powerful. BUT, it is super-reliable. That is a big bonus. My KelTec has always been reliable at the range, but in an up-close and personal encounter, things go wrong that don't go wrong at the range.
So, even though it is less powerful and holds less ammo, I end up carrying the S&W Ti-Airweight most often because it is really really lightweght, rustproof, foolprrof, just about jam-proof, and just so darn convenient.
It is not like 5 rounds of +P .38 is too bad, but I do try to keep it as my backup to a more powerful primary weapon when possible.
I have to say, I LOVE (!!!!) my titanium snubbie, and it grows on me all the time! It is so easy to carry, easy to take care of, easy to use, and so darn reliable. I am really into hi-capacity and powerful cartridges, but this gun is just so darn easy to carry, I have it ALL the time. I refuse to allow myself to fall into the trap of carrying such an underpowered gun as a primary, but there are a few times that it is the only gun I have on me, when I just can't carry something bigger.
Unlike many people, I have had to draw and fire my gun to save my life, and I know that you never have a big enough gun when you need it. So, I strive to carry the biggest, meanest gun I can at all times. The snubbie is the ultimate fallback, right before my knife, and my bare hands and teeth.