I have AppleCare+ on my watch and on my iPhone.
I had it on my previous iPone 6 and it turned out to be invaluable. Right on the final day of the two year period, it died for no apparent reason and Apple had it replaced within a couple of days.
I gifted it to my wife and got myself a new iPhone. Everyone was happy.
My main reason is not so much the warranty aspect, but more the insurance aspect - they'll replace a broken one, virtually unchallenged.