Workflowy reminds me of OmniOutliner, they share a very similar, hierarchical approach. Sadly they also share similar problems; a GUI that's too slow for my fingers and too complex for my little brain.
The GUI-complexity stems from the enforced hierarchy. Indenting stuff seems nice at first, and makes it look tidy. But after a while I'd find myself constantly futzing with the indentation in the futile attempt to structure what doesn't want to be structured.
And finally workflowy has the added drawback of living inside the browser - which is not nearly as close to my fingertips as a native app.
For me NV is ultimately the better approach. I can not praise it highly enough. Think: "full-text search for your brain". Try it out if you haven't yet.