Dear Dieter, first of all congratulation on the successful surgery, and getting some relief from pain. I too wish there are more studies/reports of long term comparisons of the artificial discs!
If you search for cervical ADR & Heterotopic ossification, you will find some studies that compare few ADR's in terms of post-op ossification. But I have not seen a comparison of the discs in terms of their reliability and long term durability! Attached is what the M6 company provided, and there are others.
In terms of ADR vs. ACDF, there are many studies, I like the following two, as they compare the results form several other studies, and both are consistent with your findings, the differences are not statistically significant:
For me personally, I prefer the ADR approach, because in case of future issues, it can be removed and replaced with ACFD, where with Fusion I do not think it is possible to revise it later to ADR!
Best wishes,
Dema