sfx2000
Part of the Furniture
I can vouch for this! In enterprise 80MHz or higher is nothing but marketing. It's useful when in an empty space, but in a crowded area, 40MHz is the only option. Even 20 for 5GHz when it's a dense population.
On 2.4...considering the number of channels available, 20 is the only option. That only if 2?4 is needed.
With 11ac - 20MHz channels there's no real benefit, might as well stay with 11n - highest MCS with 20MHz is MCS7 (because MCS8/9 numerics don't work there). There's a knock-on benefit for the older client stations as well - 11n and 11ac coexist much better than 11 b/g and 11n do in 2.4...
11ac can work very well with 40MHz channels - for business type workloads, most folks wouldn't notice the difference. The benefit of 40MHz in 5GHz, and 20MHz in 2.4 - in retrofit/upgrades from legacy, one can drop in the new AP's and reuse the frequency plan that was in place with older 11n AP's.