Well, screen-wise, both are the same. Its just that M96 is a new device & going forward, Android is the platform of choice for Onyx, so you can expect more development on it, more/quicker bugfixes & features. As of now though, M92 has a bigger install/user base, but M96 should play catch-up with time. Currently, you might want only PDFs, but with time, you'll want more from the device & with a view towards the future, M96 looks a safe(r) bet.