Elo loss for resign vs checkmate Is there a difference in the amount of ELO a player loses from resigning versus being checkmated? 

If so - What is the difference in the calculation?
No difference whatsoever.  As with tournament results, ELO (or Glicko, or any other chess rating system) counts all losses the same, all draws the same, and all wins the same.  Doesn't matter if you lose on time, resign, or get mated on the board --- nor whether it took 12 moves or 120.  Likewise a draw is a draw, whether by agreement, repetition, stalemate (either side), or even the 50-move rule.