Detailed settings. Full-on campaigns, sandboxy adventures.
I'm actually pretty bad at coming up with my own settings and campaigns, so run 99% published adventures. The lack thereof means that NEW (and, by extension, the OLD and NOW system) will get to sit in my computer unused for now, unless I get one of my increasingly rare inspirative moments where I churn out an entire campaign over a week-long, caffeine-fueled writing fest.
Haven't had one of those in many years, though...