I think you have to consider that many amps were designed with a particular power tube in mind, so that although we can describe a particular tube's characteristics, it's also the combination of circuit design + the tubes = tone.
that said,
6L6's ..... big and round
6V6's .... like a smaller version of the 6L6, with a little sweeter crunch
EL 34 .... yes, sweeter overdrive
EL 84 .... crunchy, even snarly, a little less bottom, with some inherent compression under gain. Sweet top end with lots of harmonics. Unlike the others here, it also has gain.