Angel was good for Buffy, Spike was good for Buffy. But only in the time that each of them had a relationship, as Buffy was growing as a person.
What did Buffy get, a scythe and what good was it ? it made killing the Turok-hans easier.
Who did Buffy want to help her in the battle against the first, she took Angels pressie then told him 'to go forth and multiply'. Or was it start a second front, yeh right !. She'd seen what she was up against, would she have wanted the best army possible ?, so why tell Angel to go away ?.
It was Spike that she wanted to help her.
Now it was the amulet that saved the day, Buffy didn't want Angel to be there, she wanted Spike.
Who was with her the longest ? They both had a relationship with her, but then the length of time isn't a contributing factor.
As for the names Bangel.....Spuffy.
With Bangel Buffy has only one letter where-as in Spuffy, Buffy plays a more major part and as I see Buffy to be the contributing factor here Spuffy would have to win.
For me I'd prefer her and Faith but as Buffy said,' we're just good friends really'.