I've used the OEC Elite CFD at IPSIS training, and we have both an OEC Elite CFD and a Zenition 70 at the hospitals I've trained at. Never worked with Ziehm C-arms. Both models previously mentioned are excellent. The Zenition is cheaper and tends to use lower doses, but the images are slightly better with the Elite CFD. The Elite CFD is the best but also the most expensive C-arm I've worked with (although that would technically be a Philips Azurion Biplanar we sometimes end on that's actually awful for pain cause there's no filter for bone).