It's a bit academic nowadays, as watts have become cheaper and more plentiful. As others point out, the difference between 50 and 500 watts is only around twice the volume (depending on speaker efficiency, eq choices, etc). And that's before you get into the minefield that is wattage, how much difference quoted/claimed figures actually make and so on.
Class D has meant high powered amps are small and light, so there is no longer a need to have large and smaller amps. I use either of my heads (700w or 1000w claimed) for practice and small gigs with one or two cabs and keep the volume down. If I need to make more noise, I simply add more cabs and turn up the wick.