Firmware for Hi10 pro models prior 2017

[goofieshot]

My 10 pro models came with 5.1 firmware and I am sure that their performance was optimized for that version. Considering that there are new model out there running 7 and have hardware that can fully utilize it - is there any performance or options lost when older generation 5.1 unit is upgraded to say 2.1.7. I am asking because there is a lot of info here but this is not mentioned. It is treated more as preference. Thanks for all your info.