Shot gun is the best home defense weapon, but if you're dead set on getting a handgun without a lot of kick I would suggest a 9mm with a 4.5 to 5.5in barrel (if you're not going to CCW it).. The smaller the frame the more recoil you'll feel. The 40S&W will have a little more stopping power. My Glock 22 shots great, but I always seem to go back to my Ruger P89 when I'm just plinking. Less kick, cheaper bullets and just as reliable and accurate as the Glock... Stay away from the Saturday night specials or disposable guns.. If you go with a good name brand you're more than likely going to get at least what you paid for it when you go to sell it. You get what you pay for.
I would also suggest that you go to blackwing or Powder room and rent a couple different guns to get the feel for the caliber you want.