Adorama, like B&H, is one of big online retailers in the NY area, They have been around for years. I just used their killer deals to get a 2013 rMBP with AppleCare for $600 off the combo...and naturally no sales tax or shipping charges.
Simply compare the terms and conditions (T&C) to both policies. What types of problems are included? What about accidental damage? On this site we often hear of folks spilling drinks onto the machine or dropping it. AppleCare will not cover accidental damage. Indeed Square Trade may be a better policy for repairs.
One big advantage for a Mac is you can walk into an Apple store if there is a problem. That may or may not get you a faster repair.