Do you already know the Wiki? Compare for yourself:
wiki.mobileread.com/wiki/Sony_DPT-RP1
wiki.mobileread.com/wiki/BOOX_MAX2_Pro
I don't own any of both devices, but the Onyx Boox appears to be the better option for the money, both for the hardware and the software capabilities. The Sony device is too limited unless the rather narrow scope of functionality matches the intended use scenario.