Quite a dilemma, though I don't use scribble has nice features (and its faster?). HTML5 tools have much greater reach tough. I guess something ideal would be auto switch to normal text if html5. Saw some consideration for html5 in scribble code so I thought it might work.
As for features, I also meant integrating other's element (if worthy) Just made a range bar (off the Progress bar) and I'm thinking about dropdown menu & rearrangeable Lists. Wouldnt want to attempt those if you were also planning on it.