John and Paul's voices are the best.
They're really similar. John has a great low voice and can reach high pitches with big harmony... Paul's can steer to various sides - he can have a low voice as greatly as he can have a high voice.
The pitches in both voices are similar and that's why I find it a bit hard to choose.
There's a bit of a nasal condition in John's voice and this adapts perfectly to some songs, but Paul has a great way of combining his voice to the melody of the song.
So I rest my case saying they're pretty similar and hard to choose a better one.
And also some credit to George Harrison and Ringo Starr, who just don't get a spotlight for their voice because they rarely sing, but when they do they also come out with a great pitch.