Neither, Among quqlity in the same class the ones with external Antenna are better bet.
If you are a ""Penny Pincher"".
Get this - http://www.newegg.com/Product/Produc...w&gclsrc=aw.ds
Otherwise - http://www.newegg.com/Product/Produc...82E16833320115
Agree except the AC66 has a slower CPU than both the A56 and AC68.
Amazon has the 68 for the same price as you linked the 66
http://www.amazon.com/RT-AC68U-Wirel.../dp/B00FB45SI4
The prices vary quite often and some deals can be had.
If you have a t-mobile account you can buy a t-mobile branded ac68 for $100
http://slickdeals.net/f/7193262-t-m...c-router-by-asus-free-for-postpaid-25-deposit