Leeds to Manchester Airport by train is an excellent journey
...Cough! You must be joking, endless delays and cancellations, worse now that the new timetable is in force, huge overcrowding at peak times (easily worse than the London Underground), and to cap it all off the trains are dirty, staff unhelpful and if by chance you might want to actually travel to or from the airport at night, you have a good chance of finding yourself on a bus for at least part of the journey.
I concur, however, that the alternative (M60/M62) is not much better.