Has DL ever flown 777 SFO-ATL?? It's certainly not regularly scheduled. I've been on A333 on this route but it's very sporadic. Most of the time it's B739 or B75x, though I think the A321 is making appearances now.
MSP might be a good choice only because it's the shortest flight, so if you miss the upgrade you don't suffer as much (especially if the ATL flight you're considering is B739).
I think you're right I was confusing the relatively rare A330 on this route with the 777 ATL-LAX that continues to SYD.