Actually, their stats are pretty similar, despite Lyon playing half his game in Aus, which is supposedly "the off-spinners graveyard". Personally I think Lyon is the more talented and flexible bowler. Swann quite often cleaned up the tail after Anderson and Broad had knocked over the top order.
We're going to have to agree to disagree here I think; my view is, Swann ran through good sides, Lyon does not. Swann was influential in a series win in India and an away Ashes victory - things Lyon is only dreaming of. Swann was a match winner. And, crucially, Lyon only matured into the idea of a test bowler once he had the biggest, nastiest pace attack ahead of him (Mitch 1, Mitch 2, Hazlewood, Cummins etc)...
Thats not to decry Lyon's improvement, or his brilliance as a man to tie up an end. But in English terms, he is more a Giles or Leach than a Swann.