Well I can´t work with the little display and everytime in post my picture is too dark, so I need a monitor that shows my live view in the right brightness. Also it should be able to record, so I need a HDMI Output. And I´m not sure if I need a Full-Hd screen. Is a HD Screen enough on a 7inch display? I´d like to have a sharp display.
As I´m shooting in S-Log-2, I have seen some monitors where you can put a Lut over it while filming, this would be a nice extra but no need. I hope that answer your question