Small semi-auto's are more difficult to shoot for people with little experience, and people with little experience will often find them hard to keep running. If your level of experience is low, then I would not recommend either one. What I would recommend, if this happens to be your situation, would be a small used revolver such as a Ruger SP101 or similar. Start off with .38's, and then move to .357 when you are ready.

If however you know how to handle and maintain a small semi, then I think they will both serve you reasonably well. I would be more partial to the KT as I have a P3AT that has performed very admirably. I also don't typically recommend Taurus semi's for defense use (though they make perfectly adequate range guns), but their revolvers would be worth looking into.

Another semi to look at is the CW9 from Kahr. It is a better pistol than the two you mention. I don't know what the price difference is, but you can easily find out. Other than the CW, the only small and readily-available semi's I would recommend would be a used Glock 26, Springfield XDc, S&W M&P9c.

Almost forgot to add: I have used a PF9 one time. It was ok overall. Reliability with fmj for the short range session was 100%, but that was only over 100 rounds. Accuracy was decent - not good enough to make me happy, but good enough for short-range defense use. Trigger was mediocre.

KelTec and Taurus both seem to generate a love 'em or hate 'em relationship with the people who buy them and more so with people who have had friends who owned them. Both manufacturers have had problems and both, if I am not mistaken, offer lifetime warranties.

I've owned one KelTec which was a perfect paperweight - not much good for more than that. I sold it and never considered a KelTec again. My Taurus 709 has been flawless through 600-700 rounds and I trust my life to it everyday as it is now my EDC. 10 years ago I wouldn't have even considered a Taurus for a range gun but they seem to have made great strides in quality. Since buying the 709 a few months ago I've purchased two other Taurus guns and both have been flawless.