50/50 cloudy/clear is peak THC according to Jorge Cervantes so earlier has more of a head high. Lots of amber trichs give more 'couch lock' as the amber indicates the THC is breaking down into CBN which promotes sleep. Of course that is strain dependant so a sativa dominant will still give lots of head buzz even when going amber and some indicas will floor you even if picked early.
Many strains colas fatten up a lot in the last couple weeks so picking early can drastically affect yields as well.