the cranks are different. The chain rings are different. The Red RD has full carbon cages instead of just 1 plate like force, and the brakes are different as well. Ceramic pulleys yes - as for BB - as mentioned the ceramic option is available for all SRAM cranks just like the steel ones are available for all cranks - even Red. Don't forget the ever CAD/CAM-tastic 1090 cassette over the Force/Rival 1070 Cassette, Ti front derail cage that flexes like a young gymnast. .....and zero-loss.....but yeah....Zero-loss is the only real difference.....if you ignore almost all of the other parts of the group that is...

In all seriousness though Zero-Loss is the one feature that I recommend to all of my clients to splurge for. The rest I usually spec out as Force and Rival mix. Personally the 1090 cassettes have worked their way into my personal setups and I ended up with Red chain rings on my Quarq.