I don't have any hands on experience with either, however I do know the Ratio Eight had some minor problems with the units out of their Kickstarter. I have no idea if those 'known' issues were fixed...
I personally purchased the Bonavita BV1900TS... it has a nice thermal craft when I'm brewing larger amounts. If I want to use my Chemex I simply prepare like normal and use the Bonavita. On this particular model the brew basket sits on top of the thermal craft. So simply remove and place your Chemex under the shower head... works perfectly.
For single cup the only good option is the Cup-one. From my research and experience the brewers designed for larger 20-40oz don't do well for one cup. If you want more than that... probably best to go with a smaller Technovorm or Bonavita... at least that would be my decision.