I like this idea of reviewing soundboards to compare them.
I think a spreadsheet style, with features on one axis, board names on the other, would be nice.
An open-source board and code will always be evolving, so it may be unfair to compare against private /propietary code. Maybe one day the PL boards will join in the orgy and allow interaction across platforms.
I have used a NBv4 and Teensysaber.
The biggest advantage in my mind for PL boards and NBv4 is the tiny size and dead simple wiring.
In my mind, those choosing to use the open-source boards are doing so to learn new skills. Once you wire an arduino or teensy up, all the other boards seem easy.
There are smaller players not mentioned, that are developing their own boards , which should be reviewed.
I doubt I will ever purchase a single font soundboard. Honestly, the Toy hasbro Obi-wan clonewars board is comparable to the "professional" single font boards. Throw a 2 watt pre-amp in there and you have a loud board capable of powering 2 dies at full power and 1 with speaker flicker.
Both Teensysaber and NBv4 are loud and the sound quality is similiar(same bass speaker).
The NBv4 is cool, it fits in tiny hilts.
The teensysaber is epic. The options and sound and the learning I experienced is amazing. The support and patience from Profezzorn is awesome, not even a little salty (which would be tough to resist in some instances!) I'm glad I challenged myself to do it.
The play time is decent if you don't use a white blade on steady.
Next is to figure out the arudino saber!