Una Due Tfc
There are few variable to look at
1. The airfield layout, taxiways, and runway exits
2. Mix of traffic
3. Actual needs of traffic (ie does it all arrive/depart similar times)
Manchester between 06.00 and 10.00 and in evening has a huge demand with about 50 plus per hour with a large mix of aircraft i:e Dash 8 then B747 Then EMB-175 for example, this causes big gaps which Gatwick suffers much less as most aircraft are A319 upwards, could MAN operate on one runway ask the ATC guys but I very much doubt it on an hour by hour day by day basis
I remember many times before 2 runways as many as 12 at holding point and as many in holds waiting to come in which I know for certain made the controllers eyes water and the airlines.
Ian