Flybe
Bagso
To add to Adfly's post it also depends on how you spin the numbers.
A quick look at June shows BHX has 11 based aircraft, more than double Manchester and 50 mainline flights on average per weekday compared to around 47 for Manchester and 8 jets based at BHX to Manchester's 3.
However when you add in the Loganair flights (GLA & NWI) then Manchester outstrips the BHX mainline flights and there is a distinct possibility there could be further consolidation at BHX as the schedule on sale makes no sense.
BHX needs 11 aircraft at times but this is with one 175 sitting on the deck until 5pm and a Q400 departing at 10.25 on its first flight. That simply won't be allowed to happen and I will assume it will mean 9/10 based at most unless they are going to increase frequency of existing routes or add some new ones.
The likely outcome is that BHX will remain the larger base in terms of aircraft but in terms of flights and seats available it will be close. I guess more will be known once the BHX schedule is adjusted.
Pete