The best gun is what you are trained and proficient with. I have an M&P fullsize 45 with HST's and a TRL-1 mounted on it. I shoot this gun regularly so its the best for me. I live in a neighborhood of houses on an acre each so we're fairly close to each other, misses could be a bad thing. Otherwise my next most proficient weapon and first choice would be my ak-47. I have no doubts with that rifle taking care of business.
I guess my point is train with what you have and be proficient with your weapon. Most important is make your house as secure as you can, don't be an easy target.