The biggest advantage of the AR15 from my perspective is it's versatility. Caliber changes are as often simple as getting a new upper receiver. Add optics, lights, suppressor, or other accessories easily.
As far as caliber goes, I'm not the biggest fan of the 5.56mm. But, there have been some really great developments in that caliber over the past 40 years. There are loads specifically developed to NOT penetrate walls. Other loads will reliably kill any game up to Deer. You name the application, and someone has ammo for it.
One of the biggest advantages of the AR15 is how easily you can use it for inexpensive .22lr practice. CMMG makes an inexpensive, reliable kit for under $200 for use with any 5.56mm upper. The mags are a pain to load without the loading tool. But, extra mags are not terribly expensive. I carry five to the range. When they are empty, I change uppers to shoot a couple of magazines of 5.56mm.
For hog, deer, or longer range shooting, I have a 6.5 Grendel upper. Ammo can be pricey and hard to find. But with online shopping, there are a lot of options.
Another huge advantage of having an AR15 is that you do not have to practice with multiple platforms. No matter how you change it, the selector/safety will be the same, the grip will be the same, your cheek weld will be the same, magazine changes will be the same. For rifle that will be used for both hunting and home defense, that is a HUGE advantage.