ZYX R100 or Dynavector 20x2 L?

Have you checked Vinyl Engine's Cartridge database to confirm that both carts will work well with that arm in terms of resonance? That will be an important first step.

@ Roscoeiii: thank you for the imput; I checked on VE's database and both carts are suitable for the rb700

I am a big fan of both ZYX and Dyna, but haven't heard either of these models. Don't think you'll go wrong with either.

What cartridge are you replacing? The ZYX R100 could be to lean sounding depending on the balance of your system. The Dynavector 20x2(low) is a solid allrounder. FWIW some claim the 20x2L has some of the characteristics of the Transfiguration Axia($2495).