I've won plain Azeds 4 times and have had 3 VHCs and about the same number of HCs in competition (ie clue writing) puzzles.
Other wins have been the Spectator (4 or 5 times, I forget which) and one each in the Grauniad, Generalist and, most recently, Mephisto.
I think it's totally luck of the draw in most cases and if you keep plugging away and getting them right, you'll be picked eventually.
I'd love to win the Listener, but it's totally beyond me most weeks so that's unlikely to happen.