Little known fact, did you all know that the same guy who did the initial designs for the Glocks also created the xd? I have a Glock 21 as well as various other handguns and I cannot tell you how much I love my Glock. It is so easy to field strip, it needs no upkeep, they are durable as all get out, and they are extremely accurate. If you are planning on just shooting it at a range and aren't looking for a ccw weapon I would definitely go for a full size gun instead of a sub-compact because the larger guns are more comfortable to shoot for long periods of time. As for caliber, just pick something that you will enjoy and get good with. I personally have multiple .22's but would never suggest one for self defense. I know a guy whose house was broken into and he was shot three times in the chest with a .22 and he chased down the attacker and sat on him til the cops came lol .22 doesn't have any knockdown power. I personally have a .357 mag, .38 special, .380 auto, 9mm, and a .45. I personally like my .45 best although the .357 mag is wonderful and it can shoot the cheaper .38 special ammo for practice. My friend is an avid 9mm guy and when he finally shot my .45 he emptied the mag, handed it back to me and said "Your gun definitely has a bigger p e nis than mine." I lol'd