One difference between Spike and Angel is that Spike is able to see evil Spike as a different person from 'Souled Spike' and thus even though he does feel guilt for Evil Spike's actions he doesn't feel the need to be redeemed, as he's never used his free will to do anything evil.
The battle can't be finally won and all evil eliminated forever, and that's what Angel finally accepted when he signed away the prophecy. Even though he saved a whole lot of lives in all his minor victories. It's just bizarre that the prophecy works that way, that it can just be turned off. It's kind of interesting that the vision given to him by Cordelia led him to lose the prophecy, like TPTB intentionally led him to disavow the reward they promised him.
The battle can't be finally won and all evil eliminated forever, and that's what Angel finally accepted when he signed away the prophecy. Even though he saved a whole lot of lives in all his minor victories. It's just bizarre that the prophecy works that way, that it can just be turned off. It's kind of interesting that the vision given to him by Cordelia led him to lose the prophecy, like TPTB intentionally led him to disavow the reward they promised him.