The truth is Stansted will always be a better airport than Luton from an infrastructure point of view . It was rebuilt on the opposite side of the runway from the old terminal because it had the land to do so and has plenty of room for further expansion.
On the other hand Luton has to keep upgrading its existing footprint with infill. Squeezing a quart into a pint pot comes to mind with the odd extra stand being created here and there and the terminal getting the same treatment.
Both airports have been remarkably successful in recent years but sometimes I think people here view airports like a football league table and position is everything while the passenger experience can be ignored.
Luton is above Birmingham but after visiting Birmingham I was surprised how good that airport was from a passengers perspective. Lets all remember that Luton came bottom in the recent Which passenger survey result. Stansted can't gloat as they came second from bottom out of 35 UK airports.
I can't see Luton moving from bottom in the next 2 years with the terminal about to receive an influx of builders but after that the big goal is to improve the customer experience.