I am decidedly a handgunner first and the majority of my firearms training time and effort is spent on the handgun. However, there are many things that only a rifle can do and keeping a dedicated defensive rifle available, at least in the home, is in my opinion best practice. The shotgun also has its place as the king of close range power. I have found, however, that a modern carbine with a low-powered magnified optic is the most versatile single defensive long gun setup for my purposes. Obviously it may not be so for everyone, but many would probably agree with the efficiency of this setup. A lot of shooters think of magnified optics only in terms of higher powered scopes, perhaps the ones they have long hunted with. These are great for long range accuracy but crap for close in speed. Well, the newer generation of variable power optics that do true 1x on the low end are a whole different ballgame.
Every weapon is a niche weapon that excels within its niche and is limited outside of it. The shotgun is a great example of this, absolutely devastating within buckshot range but fairly limited beyond it. A rifle like the modern AR15 carbine variant is, in my opinion, more versatile as an overall weapon. It does not have the power or enhanced hit potential of the shotgun within closer range, but it hits much harder than a handgun and it offers far more range, accuracy, and ammunition capacity than the shotgun. It is truly versatile. Beyond just the selection of a rifle, however, we must deal with the selection of a sighting system.
The red-dot sight, such as the excellent Aimpoint series, has become industry standard and for good reason. Red dot and reflex sights offer unlimited eye relief and they are very fast on target. They offer a single focal plane, as opposed to iron sights, making them faster. The use of an illuminated dot makes them excellent for low light. However, I believe the newer breed of 1x scopes that also have illuminated dots prove more capable for a variety of uses.
I find that a scope that is truly 1 power on its low setting (many are actually 1.5 making them a bit slower in close range target acquisition) is as fast as a red dot at very close range if the scope has good eye relief and eye box. A more consistent mount and cheek weld needs to be obtained, which is obviously still a disadvantage compared to the red dot. However, once you start reaching out in range it is hard to argue with the advantages of a magnified optic. If a rifle is strictly a home defense gun that will be used only at close ranges a red dot may still be the way to go. However, I find that I am equally as fast with a good true 1 power magnified optic under most circumstances and for farther shots the magnification is, again, an undeniable advantage.
The second thing that I like about the low-power variable scope is that the reticle is always visible even when the electronic center dot is turned off. If you have a red dot optic and the electronics die, which can happen even with the best of them, then you have no reticle. The solution here, of course, is to have co-witnessed backup sights. With the low-powered scope you have the sighting reticle available even if the illuminated dot goes dead. This is an advantage and a new, good quality scope makes for a very reliable sighting platform.
Finally, this setup proves versatile enough to do pretty much anything a rifle is needed for. Home defense? Absolutely. Ranch defense? Yup. You can hunt deer and other medium game with it. You can jump out of your truck and zap a coyote 200 yards away with it, no problem. And you can handle two legged threats with aplomb, even when it is close in and fast. A carbine with a true 1x magnified scope with an illuminated reticle does most things well.