I haven't been to the Manchester arena,so don't know the AO. However building design will play a big part, I know the Glasgow Hydro, is much more adaptable than the old Glasgow SECC so is easier for different types of events, and can close off sections easier for smaller capacity events.It also has far better acoustics which will sway bands too.
I'm assuming all this has been thought of and incorporated into the Coop arena and will be difficult for the old AO to compete with.
The Coop Live Arena is more adaptable than the Hydro Arena. Floor layouts previously posted from the planning application.