Ummm......good luck with "best" when talking tires, oil, and gas....It's a passionate topic. Anyways, all depends on what you want. What do you mean when you say "Best"? Are you talking grip, traction in corners, over hard packed, sand, long milage, don't hum while at 70mph.....you catching my drift?
Tires I like (I'm NOT a pro) are K-60's, MotoZ, TKC80's. I would even use a combination of these depending on what I think I'll be riding. My personal view is I prefer a balance of milage vs traction. Personally I hate changing tires every 3000miles even if they are considered "the best". A TKC80 front and K-60 rear is what I've used on other big bikes and it's been great.....for me. Others will disagree and thats fine. I think its a personal choice and one you might have to explore yourself.
Not sure how the AT will use tires as some bikes just chew tires up while others seem to be a bit easier on them. Good luck with your choice.
Don't threaten me with a good time!