Ashley The initial preview on NW.js appears to take ~1 second longer than Chrome. Subsequent previews (reloading the existing preview) take the same time.
Generating the preview is fairly quick; 2.5 seconds and the game window is there.
Loading the preview (with percentage or progress bar in the game window) is what takes the longest, at about 4.5 seconds.
So all in all it takes about 7 seconds for a fresh preview.
Approx. download = 17.7mb | Memory use = 7.2mb
C3 will probably be out by the time this becomes a real problem (for my team, at least) but if it's not too much trouble I think any preview optimizations will be appreciated!