Teleporters have the advantage of fast and easy power/advantages immediately. Assuming a teleporter just figured out he can teleport anywhere, and he fought a person who just realized he's immortal, the teleporter can win easily. He just teleports the hapless immortal into a really hot place, underneath the earth, or deep beneath the ocean, then warps back out. The hapless newly immortalized guy won't know what hit 'im, and will stay stuck for an eternity.
Immortality brings more possibilities to the table that even those with teleportation cannot fathom. Assuming an immortal has aged enough and used his immortality well, he could learn arcane secrets, developed technologies, or made friends with people you normally couldn't in one lifetime. Not to mention all the experience - you may be able to even predict the teleporter's jumps in the fight and work against it.
Not to mention that if the immortal has gotten used to the fact that pain is meaningless, the usual teleporter trick of sticking him somewhere won't work - if for instance, he grabs hold of the teleporter much harder than a normal person would, without regard to his fingers or joints/muscles. The teleporter would have a harder time getting rid of him as a result.
I'd choose immortality in this case.