Hard to choose. Overall I prefer to watch my shows weekly cuz I like to take part in community active disccussions, or simply go with the hype/rant train as it rolls.
It depends. If a show is really good, I will watch it weekly. Sometimes I put a show on hold until BDs are out. But sometimes I just look for older anime, if newer anime is just crap.
In general I am watching anime weekly, but sometimes I watch missed gems after completion. And tend to avoid the shows that I follow on manga form (unless the anime is a must watch, like FullMetalAlchemist on its time)
Unless the series is completed I watch it weekly granted it's a really good anime and I can't wait for the next episode. Otherwise I let a couple episodes accumulate and watch them all at once.
Used to watch them weekly and the anticipation of waiting the next episode to know what's going to happen, is unbearable. Now I usually watch an anime or series when they're completed, per season though. Not after the whole series are released.