My opinion. If you were going to keep the Rega then go with the Benz. If you are planning on upgrading the Rega in the near future then go with the Dynavector.
Just my opinion and you have narrowed it down to two good choices.
Jim
Benz Glider vs Dynavector DV-17D3 phono cartridge
I have a Townshend Rock MkIII table with a Rega 300 arm. I am currently using an older Glider high output cartridge that I need to replace. My phono preamp is the Ray Samuels Nighthawk which can accomodate a low output cartridge. I value midrange purity in voices and a lively, true to the rhythm sound. I listen to a wide range of music from symphonies to folk. I am looking at cartridges that I can secure in the $1000 range and right now am looking at the new Benz Glider or Dynavector DV-17D3 cartridges, but I am also open to other options. Appreciate any suggestions. Thanks