I'm gonna assume you mean elven immortality vs. invulnerability?
I say elven immortality, because those fuckers are immortal, but they can still die from injury and sickness. Regular immortality is a kind of modified invulnerability.
I'd rather have invulnerability because it would be awesome to do whatever I wanted for the duration of my life. I would do quite a bit of lava swimming, get shot out to space, re-enter the atmosphere, walk on the moon, and basically did whatever I wanted.
If I was immortal, I'd become a recluse (so people would leave me alone) and become a writer. So, basically my current plan, but with much less social interaction.