FRA is weak, often crowded with minimal food choices. SFO domestic and international are among the best domestic RCCs (I'd honestly choose either over FRA) or you might decide to spend your time in ORD, although those can be crowded as well.

I suggest you decide where you think it will be of greatest benefit during your trip. As for me, FWIW given your itinerary I'd probably plan to visit the SFO domestic (no arrival access to the International RCC) after clearing Immigration and walking over to the domestic terminal. If you decide to get a bite to eat instead and wander around a fairly pleasant SFO environment, you could still use the pass in ORD after check-in.

Cheers,
Fredd