tbakko,
If they're both choice, or both prime, the only difference is the price (and bone in/no bone)--in my book.
I just bought 4 "Choice" standing rib roasts (avg 5.5 lbs) yesterday for $5.99 per pound (bone in). That is me stocking up for a few months at the best price I've seen in my neck of the woods in years. I got 3 last year for that price too (smoked the one and was better than any "Prime Rib" I have ever had).
Most of the time around here, the standing rib roasts are "choice" bone in, and the "Choice" Ribeyes are cut into steaks, without the bone.
The best price I ever see around here for them is $5.99 for the "bone in" standing rib roast & $6.99 for the Ribeye steaks.
If those are choice or better, I'd take a freakin' wheelbarrow to that store quick!
Bear