What does "better vocalist" mean to you?
Assuming that the person can sing on key what is that you mean by "better vocalist" as opposed to a vocalist whose style you like more.
Wider range? Advanced technical abilities and vocal acrobatics? Soul(bringing emotion to a tune)? Timbre?
To me once a person has a decent range and feeling, there is no "better" there is only "preferred"
How do you see it?
"These lifeforms feel such passionate hatreds over matters of custom, God concepts, even - strangely enough - economic systems." - Capt. J Piccard USS Enterprise
Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate; only love can do that. - Martin Luther King, Jr.