The solid advice is that the 50 watt speakers will probably produce a a more accurate sound (at higher volume)

And yet they may well end up producing a less accurate sound at lower volume. As Flatline pointed out, more power capability will (usually) involve more cone movement and more mass to move, requiring more power from your amplifier for the same output.

Sure, the speaker may be able to accept more power than the lower-rated one before the smoke leaks out, but it will also require more power to make any noise at all at the other end of the volume scale. It was precisely for this reason that we decided on 250 watt rated subwoofers instead of the higher-end 500 watt subwoofers for my ShoWagon. I only have 300 watts total for the subwoofers, so having a pair of subs that could eat a total of 1000 watts was a bit of an overkill.

tanstaafl.