he should become human!!!!
Just because Angel has suffered for hundreds of years (and hey--he didn't ask for that suffering either people, it was burdened to him) does not mean that he is the deserving one of becoming human (And I'm not talking shanshu~clearly it's hard to believe in the shanshu prophecy... both the vamps have saved the world, Spike has even given up his 'life' to save the world... and nothing. I'm talking just everyday magic or what not here.)
We have seen Angel as a mortal human...and it sucked! Remeber? Angel could not handle it. He much rather prefers to be a hero, with the strenght and ability to protect the world. That is what he is most comfortable with. He can't handle being a human.
Spike, while only having a soul for a little over a year, has not yet tasted what it was like to be a human, losing his power. Spike may not have done as many good deeds as Angel (hmm... over a hundred years with a soul vs. one year with a soul. Of course there is a difference) But may I remind you,there are some times that Spike has helped out without the presence of a soul. Now, I understand that most of the times that he helped out he was influenced by the chip, and chose to help Buffy because that was the only thing he could do. I suppose Spike fans will never convince Angel fans that this still does make him somewhat good, pointing him down the right path for ultimate goodness.
But put that way... the only reason that Angel is becoming a hero of the people is because he is cursed... he's using saving as a means to an end to help him deal with his soul and grievance. It's the only thing he can do to deal with what he did.
Yet~ remember season 2, Becoming, part 2? Spike teamed up with Buffy to help defeat Angel. No chip, no soul. Yes, he had a reason, to get Drusilla back... but nobody on the show is altruistic enough to want to help people for the greater good of humanity. Everyone is helping out because they can't ignore what goes bump in the night, they are chosen, they are cursed with a soul or they are dealing with a soul.
So, in the end, I vote Spike. Whether or not any of the vampires 'deserve' to be human (which they really aren't, because they are evil things). He died to save the world and put up with a lot of stuff and that a lot in my book.