If you're looking at a Madness of Deathwing parse, Rain of Fire will score higher, as it procs Spellweave; Hellfire does not. Rain of Fire is recommended for all three specs on Madness.
Aside from that, Rain of Fire for destro, Hellfire for demo, and Seed of Corruption for aff.
Edit: Though... Now that I think about it, Spellweave shows up separately... So.. Not sure how you got to that result.
demo uses hellfire, Destro uses Rain of Fire, Affliction spam Unstable affliction. The Hellfire is just infinitly better than the 2 others that are crap but they should gain the same procs and stuff.