And I’m late again.
Once more, double post!
My favourite edition is AD&D 1st. I already declared my boundless love for it, so I’m not going to vex you again, gentle readers.
If I should instead pick my favourite D&D (simply D&D. No “As”) edition, I’d choose BECMI. It was the first version of the game I ever played, and I still find it a very good one, particularly for novice players.