For studio work the Credo does a few things that make the workflow smooth and enjoyable, and also future proof:
Firewire 800 AND USB3 tethering, giving you all the options on different platforms. The on-board battery means that you are not relying on bus power which can be challenged at times.
The LCD stays active during tethered shooting and allows you to browse, zoom into, adjust (e.g. WB) and rate the last 10 shots.
If there is a CF card in the back, you can yank the FW/ USB cable and continue to shoot into the card.
In case you need a backup body, or wish to try a different body, or change platforms altogether, the same back can be used on similar bodies, some other bodies (e.g. RZ, Fuji 680, view cameras) or its mount can be changed to fit a different 645/ 6x6 platform. Note that if you buy the back with a Gold Package (extended warranty) you are entitled for 1 mount change at no extra charge, should you decide to switch from e.g. H4X to 645DF+
There is also Live View, not that relevant when shooting people but it's worth noting that when you shoot tethered, you can use it either on the LCD or the computer.
However as I always tell people, the best way to decide it to try, try and try some more. Only YOU can tell what works better for you, what annoys you and what will serve your creativity better.
Best
Yair