Both designs are pretty new and unproven, so it's doubtful you'll find many user reviews of either model. However, I would lean towards Miele due to their better track record.

Miele in the past had temperature regulation issues, but these were 100% fixed with new software a few years ago. Wolf has had issues with the blue enamel chipping ever since they introduced it in their ovens, search past posts on this forum for more info. The M series has a removable bottom but nobody is sure whether that will be a true solution to the problem.