I have 5 to 50w Orange amps..... most of the time, my 15w AD15 is too much in terms of volume.
But my RV50, R30 and Genz Benz Black Pearl 30, my other 30w amp) can play at the same volume too, but offer more low end, and an overall more robust, fuller sound.
I dont play metal, but wven playing blues / rock, thw extra thump of fullness of the bigger amps is lovely to hear. If course, my 50 or 30w amp can be quite a bit louder, but not necessarily so. It depends on where you set them.
I must say though..... having that extra power at hand is tempting though..... the louder they are, the better they sound.....