From León there are some buses direct to Barajas. We thought this a good option as we had a night flight and would therefore have more time in León (and less hassle basically);-).Of course nothing is simple so.... be aware that in August seats were booked up days in advance! The bus we originally wanted left about 9pm but instead we had to take the 17.30 (22euros) to Madrid Estacion Sur, hang around for a few hours before catching one of the last underground trains to the airport.
There are about 12 buses a day to the capital, some non-stop.
I went by rail from Vigo -about six and a half hours of which well over 5 are through glorius scenery.
The bit nearest to León is actually the other part and is dire.
I returned to Madrid via Ávila and only the part between Ávila and Madrid is scenic. The best part of the rest came during thick mist!
(Photo - Botines house - Gaudi)
Best way to get to Leon is by train from Madrid. Buses are a good option also.
The most interesting way to get to Leon is to walk from Roncesvalles, the Pyrenees. If you do not believe me, go and ask the pilgrim's you meet in Leon.