I have a PF-9, P-11, P-40 and a P-11 with the 357 SIG conversion. They are great firearms and Kel-Tec's customer service is outstanding. The difference between the PF-9 and the P-11 is the PF-9 is a little thinner and is a single stack vs a double stack. For CC the PF-9 is a little easier to conceal and I preferred to carry it over my P-11's. The trigger pull is a little heavy but that's good for CC. For the price, functionality and customer service you can't beat Kel-Tec.
USAF Retired, CATM, SC CWP, NH NR CWP, NRA Benefactor
To preserve liberty, it is essential that the whole body of people always possess arms, and be taught alike, especially when young, how to use them... -- Richard Henry Lee, 1787