Depends on if you want the stolen/lost coverage.
Otherwise regardless if you are on AT&T Next, AppleCare + is the better plan. Some ATT Next users are on the 18 month plan, AppleCare is 2 years, includes phone support.
AppleCare gives you x2 incidents that cost 79$ per incident (Deductible)
ATT Insurance is $7 per month plus tax and fees, and is $199.00 per incident on an iPhone.
If you don't lose your phone after 10months on ATT insurance, and you accidentally broke it, you would be paying $270.00 vs $180.00 for AppleCare. However, if you break your phone again, its $79.00 for Apple and $199.00 for ATT.
In the end, 2 years with ATT and using the insurance is $368.00 vs $180.00 for Apple.
If you don't use the insurance on either plan, $168.00 vs $99.00 for Apple.
I chose AppleCare, heck I usually don't even buy insurance, my phone is my lifeline, its like losing my wallet, its something I actively make sure does not happen. But this new phone is almost 1k retail, so, its worth it to have piece and mind.
I am also not sure how many incidents you get with ATT insurance. But for $199.00 Deductible I doubt they care about incidents.