Many apparently carry their handguns (whether the P3AT, PF9, or other) with just a belt clip and seem to have had little or no problem with it. But there are two basic arguments against it. First, clip carry, especially in a pocket, expose the pistol to all kinds of lint, dust, pocket junk, etc which can get into the guns mechanism and run the risk of a gun jam at the wrong time. A decent holster helps keep this junk out of the gun, and a clean pistol has a better chance of going bang when needed. Second, although instances are pretty rare I think, many of us just don't like the idea of leaving the trigger exposed to anything which could catch on the trigger and result in an inadvertent discharge. This especially holds true for IWB carry I think, but could also happen in a pocket if say, the trigger got caught on the edge of a desk when getting up, or many other possible scenarios. That being said, as always, each individual has to make those choices appropriate for themselves. But most, if not all, pros always emphasize the importance of a good holster which fully covers/protects the trigger. JMHO.
Jim R
