With virtual certainty, you'll be in coach. I've never been upgraded from SFO to EWR on any CO flight, the red eye included. There are bound to be lots of Platinums with full Y fares in coach too.

Advice: If you want a nicer plane, a bag of free pretzels, fly CO. If you want to get upgraded more on a worse plane with the constant fear of how bad coach is if the upgrade doesn't come through, fly NWA.

Another thing about CO: They can't hold a schedule through EWR. If you have a connection tighter than 2 hours, you might well be sorry. This problem will cost CO a huge amount of my business this year.