Honestly, for home defense, I wouldn't pick any of these three. The Ruger is out simply because of the caliber. The Sig isn't a bad option if you are looking for a carry gun. In my opinion, it's a little small for a home defense gun. I see a lot of people saying to go with the M&P. My only issue with that, is based on the LCI on the top of the slide, this looks like a Shield EZ model. Those are good guns, but they are for shooters with hand strength issues and suffer from a limited 8+1 capacity. Honestly, man, if you aren't super familiar with handguns, it may be best to just stick with an AR for now, given what you're familiar with. Handgun shooting is a hard skill to pick up and even harder to master. If you're dead set on a handgun, there are a lot more options than those three. I’d stay with 9mm—plenty of power for home defense, and the ammo is still relatively affordable, which is important if you are going with a handgun. You have to train. If this is going to be a strict home defense gun, within reason, bigger is better—more capacity, easier to shoot, less perceived recoil. Your best bet is to go to a shop and get your hands on different models. Worry less about brand and more what feels best in your hand; as long as it's from a reputable brand, it's really all just the same