It really depends on the style of music and the rest of the band. Years back I played with a drummer who was restrained enough to allow me to play a 50 watt solid state (heavy distorted guitar). If you go solid state then you start to lose tone quality the closer you get to the max volume because the damn speakers vibrate so much. So for solid state louder is definitly better. If you play metal and want solid state then a 100 watt amp is perfect - I blew my Peavy 65 watt about 10 times because the drummer I played with at the time was a monster who beat the crap out of his monster sized kit.
100 watts tube is way too loud for playing with a band unless you are playing an arena IMO. The prblem with tube is that you have to crank it up to get the best tone BUT if you crank a loud amp up then you will drown out the drummer and blow everyone's eardrums. I get around this with my Triaxis by cranking the Simul-Class tube poweramp to the max and routing it through a PDI-03. So now I can get the burning tube sound and set the volume to what ever level I want (once the cabs can take it). This way I can easily put the drummer back in his cage if he starts getting out of line

I know a lot of guys who play 50 watt tube amps and are more than loud enough.