It really seems you're being screwed over in both,
SPOILERS
Maybe I'm interpreting the endings wrong, but neither seem all that great.
SPOILERS
- Spoiler:
Like, In the link the fire ending, you're pretty much not changing anything, you're simply adding more fuel to the bonfire and on the other hand, The Dark Lord ending seems better at first glance, but really all its doing is giving Kaathe a chance to finally give the darkwraiths power over Lordran.
Maybe I'm interpreting the endings wrong, but neither seem all that great.