First of all a gun has to be reliable. That means function and caliber that will actually do what it is intended.
Second it has to be concelable (light and compact) while wearing summer clothes (here in Houston that is 9 months a year). If the bad guy knows you're carrying it's game over.
Third it has to be accurate. I prefer lasers, so it has to have laser that will fit. With picatinny rails and universal lasers to mount on them we have more choices and lower prices then ever.
This is my choice for around $400. Keltec PF-9 George Zimmerman chose this one also.