For me, there are good lyric voices and good non-lyric [mostly operatic, but some just come that way]. The world may define lyric as "folky" or "musicals," but for me, good lyrical voices know how to stay on pitch and to blend. The difference is the vocal vibrato.
I think having perfect pitch is bad for these kinds of musicians -- if the group or an instrument goes flat, singers with perfect pitch can't cope.
Good a cappella voices stay on pitch. Emily has one of those voices -- it's honey sweet, strong, and true.
Good group singers keep the group on pitch or [barring that] continue to blend. I have one of those voices [or so I'm told].
Good instrumental singers stay in pitch with their instruments. Emily's choice upstream of Susan Welch is a prime example of that. there are lots of solo musicians these days who fall in this group.
Operatic voices don't do well unless there's an orchestra behind them and are a real annoyance for any of us who try to blend a group. They're the ones that stand out in choral or church choirs. And that is NOT a compliment.
But, mostly What Duck Said above.
Just my humble opinion.
Barb