Originally Posted by Kimmo

Who's obsessing? It's not a question of an intellectual fixation when you turn into a headwind on the 15t and start to chug, so you shift to the 17t and have to slow down more than necessary because you CBFed pushing 100rpm.

I would much rather occasionally find myself a little short on range than constantly have to choose between grinding and spinning.

The biggest advantage a derailleur drivetrain has is the ability to fit a cassette appropriate to the terrain you're going to ride, whether that's on a per bike or per ride basis.