Singers tend to do better as solo artists than others of the band because their voice is already tried & true for many listeners. Notice how Slash has the singer of Alter Bridge for his solo work.

However, the one thing that solo artists lack either way is the brand recognition of the band name. There's a reason you've had multiple band members tour with their "own version" of the original act, and fight in court over who gets to use the name. Tommy Thayer used to play in a Kiss tribute band - I bet they didn't do the numbers he gets in Kiss now....