Flying trans-cons or even west coast to the mid-west, you will get status much faster on miles than on segments. A typically round trip with a stop in each direction is about 5k-6k miles and 4 segments. 5 round trips gets you silver on MQM's, but it would take 7-8 round trips to get there on segments.

Also, segments don't roll over. Qualifying on miles and going over means you get to keep the MQM's to give you a head start next year.