Full size pistols and heavier pistols usually feel more comfortable when you are shooting at a range for awhile. Lots to read about on caliber as well. Often .40 cal guns were originally designed for 9mm and don't work that well on .40 etc... For home defense you may want to shoot an AR15 as well - very easy to control and aim with a huge selection of customizations and purpose designed bullets. Much easier to hit a target with a short barrel rifle than a pistol, plus a large magazine.