I can honestly say with all the guns I've fired, if I had to have only one, it would be the PS90. It's fun (if not yet cheap) to shoot, has great inherent accuracy, superb ergonomics, and an effective point-and-click capability. The round does not have the same penetration danger indoors that other rifle rounds have, and with an effective max range of 150 meters, still outreaches the spray-and-pray of the average gangbangers AK47.
Of course, this is all from my experience with rifles. I'm a firm believer in the adage, "a handgun is what you use to fight your way back to the rifle you should have never left behind."
Present equipment is that Cuda I got at Shootmoot.