I had your same problem. I evaluated "Leggo IBS" 9.68' (that is an PB912) with a resolution of 1200x825 and first eink version. Then I thought Onyx M92 was a better choice because of the superior screen (in terms of resolution and eink technology).
When I discovered Jetbook Color I took the chance to use a color, big and high resolution EDP.
The major problem with JBC now is the firmware: if you belive ectaco will do a good job with next realese (schedule on 7h March as they promised

), JBC is (according to me) a very good choice to study technical PDF.
JBC have a noticeable hardware and a pontetial not used at the present moment.
Otherwise and if colors aren't important for you and in your readings, M92 is probably better (also because of its minor weight).
In my case some Graph would be near impossible to read in B/W and with only 16 gray levels. So I'd change my JBC for nothing
EDIT: LuBiB says he had received the update for his JBC. I'm waiting from mine