I didn't try Zorbi yet but I tried Anki a few times and I simply hate its interface. Yes, it has all the features but it is far too clunky and bothersome to use for me. Zorbi in contrast looks like it has a easy, beautiful UI that I can actually use with joy.
Yes, features aren't the only reason why people use a product, but some people (me, and many others here) do mainly use a product for its features. The lack of a comparison is somewhat of an oversight.
For that matter, there's no UI comparison either - no video showing a side-by-side diff between Zorbi and other tools (Anki, Mnemosyne, Quizlet, etc) - which, all in all, makes it a hard sell for most people who are already using an SRS, and I'm pretty sure that Quizlet has much more momentum and can acquire new-to-SRS users faster than Zorbi can.