1) Which one of the two is generally considered "better", Alakazam or Gengar?
2) If I opt to use Life Orb Gengar, is Explosion superior to HP Fire to lure and destroy Blissey and clear a path for a special-based sweep?
3) Should Hypnosis be used on Gengar? Even on the SUpPunch set, I feel bad losing the Electric-type move...
1. Gengar. While they're both extremely frail and Alakazam has better SpAtk and Spe, Gengar has 3 nice immunities to switch in on and gets perfect coverage with its STAB and Focus Blast, while Alakazam still has to watch out for Psychic types (although, they are fairly rare).
2. It really depends on whether you want to take out Scizor or Blissey.
3. I'd only use Hypnosis on a set with Substitute since Gengar is far too frail to be able to afford a miss. Sleep is nice because you can instantly cripple most Pokemon, but I'd rather not worry about it missing, even with Substitute, because hax rules my life.