i actually just picked up my 380 pocket pistol today. after looking at all the ones you mentioned with the exception of the DB and hell cat because of horrible reviews this is what led me to end up taking home my new lcl this afternoon.
Kel Tec P-3AT- felt extremely similar to the lcp, little bit rougher grip texture for a better purchase on the weapon but the trigger was more gritty. also the magazine was finicky and would only stay in the gun when put in the magwell just right which made me nervous.
Taurus TCP- best trigger and good feel in the hand however it was used and ive had a bad experience with a taurus autoloader in the past. also i couldnt justify paying more than the brand new kel tec for a used taurus that may have been sold for being unreliable
Masterpiece Arms 380- smallest of the group, maybe just me but it didnt feel like i could get a good grip on it. im 6' 3" and have large hands so may work if you have smaller hands and car get a better purchase on it.
Ruger LCP- have 2 other rugers, sr9c and sr22, with the sr9c as the gun i carry about half the time so ill admit i have a bias towards rugers on top of all their excellent reviews. good trigger, came with magazine finger extension to help fit my hand and for $20 extra i got the factory engraved model.
As an added note though i put 43rds through it after i got it and it did have 2 failures to go into full battery. however i do not clean my new guns before they go to the range for the first time and have consistently had issues with any brand of firearm during the first 50rds which is within my 200rd break in period. i expect this to work itself out after cleaning it and another 150rds down the pipe as has happened with all my other firearms.