The problem with the playback of your Sozi file,
was in the way that firefox handles SVG, rather than in Sozi.
JessyInks' transitions etc seem mostly to be controlled by java, which most browsers handle very well.
Sozi's transitions merely take advantage of the nature of svg itself, so some browsers can have trouble with them.
Try playing the same Sozi presentation in opera, Chrome...and Internet explorer, and you'll see what I mean.
My Sozi presentations always seem to play back just fine, but I have occasionally had them jump, pause,
etc, in previous versions of Firefox. I haven't tested one in Ie for quite a while, but IE isn't famous for handling svg well.
I'm a bit embarrassed to admit that I've never tried to do much with Jessy Ink.
I think both JessyInk, and Sozi are fine extensions, and serve their intended purpose.. its just a matter of what your most comfortable using.
I really doubt That Sozi has any impressive "features" that you wont find a parallel for in JessyInk.
What I like about Sozi:
I like that Sozi presentation files don't need to be arranged in layers, and simple
transitions can be easily achieved with placement , and orientation of your frame object in the Sozi poster.
I can add animations if I want to...and sound( adding sound is theoretical at this point I haven't tried it yet).
But I don't need to use Java unless I choose to. Just as with JessyInk svgs, no special software is needed for playback,
an svg capable browser is all you need. I can auto-advance my presentation frames, or let the viewer advance them.
..and most importantly, I have fun playing with my Sozi presentations.
Libreoffice impress actually does nice presentations to. Sharing and playing them back on an unfamiliar computer
can occasionally be an issue though. Also, it doesnt allow me to draw my presentation graphics, and set up the presentation at the same time.
Since I'm unfamiliar with JessyInk, and havent tried it for quite a long time, can you tell me, what you like best about it?