Which is better, a wrench or a screwdriver?
Honestly this is kind of a dumb question, depends on what you need the amp to do and what music you're playing.
Let's say you play in a punk band. Do you play punk n roll like the Supersuckers or the Turks? 800. Do you play metallic so-cal hardcore ala Good Riddance and Strung Out? Then the multiwatt.
Let's say you play in a metal band. Do you play groove based stuff like Chevelle or Disturbed? Then the multiwatt. Do you play thrash like Slayer? 800.
Do you understand why this question is kind of pointless without more info?