I see, but as I say, it's irrelevant to EasyJet really what impact moving one aircraft from Luton to Stansted would make on the total passenger numbers for each of those airports.
If you think like that then maybe if Luton's total traffic took a bit of a tumbling (whilst EasyJet are still maintaining their capacity through Stansted), that could be good for EasyJet. It may become an incentive for the owners of Luton to offer a better deal to reverse decline.
To reiterate the point I was making, in case it wasn't clear (and I apologise if it wasn't)... Moving one aircraft from Luton may only result in a few frequency reductions, possibly making load factors increase as the demand stays the same or losing very few passengers in the worst case. Yet at Stansted, it could be used to offer new destinations and ultimately cater for new passengers (as well as putting back some of what they've removed in the last 2-3 years). Therefore, for EasyJet, it "would probably not effect Luton too badly, but could have great effects on Stansted."