If you can swing it the ac680 would be better. I have the ac6 and it looks like you can charge faster than I can. I am limited to 4.5 amps on a 3s pack that is rated for 11 amps charge rate (5x2.2 amps). It takes 45 minutes to replace 1600 mah approximately.
If you are not on a low budget This charger is a good buy...
I have this charger myself. I have charged 11 batteries at one time at 20 amps in 1hr 20 min. HYPERION EOS 1420I NET3 CHARGER - 1S-14S, 20A MAX, 550W
Reg price is $179.95 it is on sale for $129.95
Love my Voltz 6250 It puts out 10A I can charge my five 6S 3000mah batteries in just over an hour. The same charger is made by Icharger called the 302B i think.
When I was buying mine I was wondering the same thing. I picked the ac6 because I was seeing a lot of bad reviews about the 680. Maybe they have straightened that out now, but I would double check that first if I were you.