Overall.
In my testing, I get better transfer speeds, both wifi and lan with stock....when i was using beta 1, the web config pages sometimes failed to load, or partially loaded. And the issue of the router getting stuck in 20mhz mode....and adjusting the channels made things worse...and at one point my lan transfer speed dropped very low....had to use recovery to stock. Been running perfectly ever since. with stock.
the AC56u is quite new...so I understand things are still being hammered out.
Personally, I would like to have a stripped down version of Asus wrt. Like other custom firmwares have slim builds and full featured builds. I often find slimmed down versions to preform better. Or...at least....a build that is pure stock with only one modification, the nice detailed Status page that is included in the Merlin builds.
(does anyone know if tomato is available for the AC56U?)
Slightly off topic
:
The AC56U with stock firmware seems to fluctuate alot when transferring files over wfi. Most of the routers I have tested in the last few years do this with stock firmware. My Cisco e300 did this, until I installed Toastman tomato build....and also on My Asus N56U with Padavan firmware I definitely noticed a performance boost over stock. That router me gave consistent wifi and lan transfer speed.....none of this fluctuating that the AC56U does...though it does burst at higher speeds...it seems to need to ramp up to full speed....when i transfer a 1gb file...it starts out at about 5MB's and goes up to 25-40MB's after several seconds....(you can see the line graph in win 8 file copy slant up and have many peaks and dips)...on my N56U, it started at about 20MB-24MB's and stayed at that speed the entire transfer...(nice straight line graph)..