What I have seen and hear isthe db9 is a ok good either it works or it is one stept above a raven arms piece . You can not used +p in it ( the gun will expold ) also the reveiwer are ok but fincky about ammo In Which Your Correspondent Breaks his Diamondback DB9 | The Truth About Guns Diamondback DB9 and +P Ammo = Ka-boom! | The Truth About Guns and the early ones had issues with pins falling out .. But it does take down like a glock.
The pf9 can handl plus p ( I would hate to fire it based on how small the gun is ) Gun Review (Take Three): Kel-Tec PF9 | The Truth About Guns
I perosnal of the two would take neither and get the p-11 as I have a bunch of s&w 59 and 69 mags I can used in it .. But if of the two I would say depending on how easy to take down the pf9 is I would pick the pf9 as there seem to be more aftermakert support then the db9 and I have hear some off things about DB arms..
Also note the recoil of either is going to be very very sharp small plastic gun 9mm you get the pic. I am a bit of lightweight on recoil so I kind of like the 938 sig as it is all metal so that helps a bit with jump..
But I should not even talk I dont own either but have done a lot of reasceres into pocket 9 as I like them and own a few .. And as for gun reivews I dont trust most of them so you will proley find one half saying this is great the other saying the other thing.
Odd question though why these ? New carry gun or to collect? There are few weirder and rarer non name brand guns like the seecamps or the rohburg 9mm ( weird little things) and a few others .