I like this question. I honestly think it does not matter if they just sing or play an instrument. My favorite kind of lineup is a lead singer,
Two guitarists, a bassist and drummer, and maybe a keyboardist. It just seems to be a good
Balance in my opinion. I think if the singer just sings, there is a possibility the vocals could be more powerful and intense. Take Hansi from
Blind Guardian for example. He sounded great while playing bass and still sounds great just singing. I still have just as much respect for him. I think as long as you are an incredible vocalist, it shouldn't really matter. Like Panzerjager said, vocals are the easiest and hardest instrument to
Master, and I believe that.