From an esthetic perpective, It will generally be clear in the morning in the PNW with less haze and clouds along with pictureesque fog in the low land valley's compared to the afternoon when haze/fog will rise making lousy pictures along with any low land moisture generating clouds. Very few routes in PNW need an alpine start. Only in spring/early summer time when one wants firm snow and to stay out of avalanches and the large volcanoes and the few large glaciers is an alpine start warranted. Every other route, do whenever barring the aestheic problems.
A few PNW mountains barely reach the "real" mountain point. No, its not the typical Rocky Mountain jokes in Colorado which are no more than giant mole hills with one difficult side, but go to say Alaska, Northern Rocky Mountains, Alps, Himalaya, Peru, Equador, or anywhere there are "real" mountains then you really, really, really, want an alpine start.
Ditto on what everyone else said.
PS. Who needs sleep? Its way over rated. If you can stay up late, you can get your ass out of bed. Takes a bit of mind bending, but... Best times to climb for my money are morning and Evening. Mid day, I want to be eating/sleeping/lounging and staying out of the sun!