Greg Lake or John Wetton

Wetton for sure. 

I prefer Lake, but with King Crimson, it's Wetton, no doubt.

There already was a poll comparing Lake, Wetton, and in that one Adrian Belew too, and Wetton was winning by a margin. But my opinion remains the same, I like Lake's singing much better, Epitaph is about the best singing I can think of, while I have always found Wetton's voice rather... just not to my taste (well, in Asia he sang OK, even if the songs were not really that great, but I guess it was because of the studio recordings, since his singing Live with Asia is also a pain in my ears). I guess even into the 90's recordings of Lake I've heard I like better his singing, even if he had certainly lost that beauty in his voice, I don't find it totally lost, just different. As far as bass playing is concerned, well, I haven't payed that much attension, but I guess Wetton bass playing is more powerful and interesting. Still, I prefer Lake in a group over Wetton.

I voted for Lake. Speaking about KC, I think generally Wetton time was better. But Lake has more specific (progressive) voice, and his work with ELP is perfect in part as well. Wetton participated in some KC best albums, his work in UK was important. Not sure about Uriah Heep, and even less - about his solo works.

Wetton without a doubt. 

Greg Lake on both counts.

Considering just vocals, it's close. With bass playing in mind, there's no competition; Wetton for sure.

My two favorite singers!!
Both stand on 15 votes while I write this and now I must decide ?
I can't choose!
And you know what? I won't choose
They are both excellent singers, and they both wrote excellent melodies, excellent lyrics and they both know how to play their instrument well.
Hurrah for John and Greg

50%!!

Probably the only thing they have in common is that classic 'tenor sings rock' vocal range that makes the output of both ELP and King Crimson so separately distinctive. Wetton clearly relished the improvisational opportunities afforded by the version of Crimson he joined, whereas Lake loathed to improvise (despite the best efforts of Emerson and Palmer to encourage this) Lake's basslines are carefully considered and composed right down the last detail and timbre employed (usually a very 'pure' bass tone which he likened to that of trying to imitate the bottom notes on a piano) Wetton's playing, by way of contrast, sounds much more spontaneous and enjoys a much more intimate dialogue with Bruford's drums. His tone is habitually guttural, visceral and borderline distorted in places. They both clearly have very differing approaches to how they see the role of bass in the music they contributed to. When push comes to shove, I prefer Wetton's voice and his bass playing strikes me as being perhaps more integral to the Crimson compositions than that of Lake's with ELP ?

BTW I think Greg Lake is a much better electric guitar player than he is generally given credit for (an avenue of his talent that had precious few opportunities to be revealed with ELP)