Both were incredibly dull and pathetic while dating Buffy. Spike was a cool, vibrant character back in season two when it was him and Dru. Angel was pretty good as Angelus in season two and is a much better character on his own show. The fact is, neither had a chance to shine while being with Buffy, because Buffy is the 'star' and to have an equally powerful male character who isn't evil would have detracted from the 'girl power' message of the show. On Angel this problem is lessened (probably due the theme of that show not being 'white undead boy power') and the supporting cast is allowed to be a little tougher and a little cooler. For this reason it should be nice to see Spike make the move to Angel next season.
Then again, every character seems to get cooler and tougher when they move to Angel. Faith had some of her best moments there. I used to hate Angel before he made the move to LA. Wes was a waste of space until he switched shows. Cordy was useless and whiney until she she moved over as well (sure she sucked last season, but she was evil and possessed so I'm willing to let it slide... I hope they bring her back to Angel).