1. Does it keep up with rapid movement? (If something fails this, it’s a total non-starter.)
2. Does the eraser on the back of my pen work? (If not, it’s very frustrating and a very bad sign.)
3. Does pressure sensitivity vary the thickness of lines? (I just find it’s a bad sign if something lacks this—tools that support pressure sensitivity seem to pretty consistently be far better than tools that don’t.)
Witeboard fails all three, badly. So no way am I ever going to use it.
Ziteboard is a bit better at #1 (though still not good), but fails #2 and #3 and has hideous latency and accuracy as well—it’s postprocessing strokes heavily, which makes sense for mouse but shouldn’t be done either at all or as much for a pen. So I’m not going to use Ziteboard either, it’s unpleasant to use.
Browserboard is the worst of the three: hideous latency, terrible accuracy, missing the start and end of each stroke, and fails all three.
I’m using Firefox on Windows on a Surface Book. I know much better is possible, because I wrote a simple, local, pressure-sensitive drawing tool some years back (in the early days of pointer events), and it worked just about as well as local apps like Microsoft Whiteboard or Krita or GIMP do. All three of these tools just seem to be making rookie errors like doing too much processing probably on the main thread, and skipping coalesced events. (Those are my guesses of the problems, as a developer that has dealt with this space.) None of them are good; Ziteboard is merely the least terrible.