Might not apply totally, but here's my experience.
I built a 12wpc 6l6 based Class A amplifier. Not for guitar but for my Ipod. It had an ultralinear winding.
It sounded so good and so detailed that I'm using it now as my alternate amp for my studio. You can hear everything.
Nice thing about Class A is that it does not cancel out harmonics like other push-pulls do (AB and B). Thus you will get a more sparkly sound and more sonic detail, at least in theory (individual ears are a different matter).