This one will have the advantage of a more convenient UK airport, closer to London and with a bigger catchment area.
Maxjet & Eos chose Stansted as it is conveniently located for the "City" of London i:e; Canary Wharf as well as Cambridge which has a big market for transatlantic business travellers due to the nature of a lot of companies in and around Cambridgeshire.
If Luton was nearer and easier to get to from the City then I would have chosen to be based there as I live in the city and can tell you Luton is not as convenient for me to get to as Stansted in terms of ease of travel and distance. Some of you guys should try it and see for yourself. A lot of people on here just don't seem to like to see Stansted doing well and think the whole aviation universe revolves around Bedfordshire.