Not an expert but here are some thoughts.
The ‘14 and older OEM computers don’t do any fan controls, but the ‘15+ can control a single fan. I am sure the Terminator does fan control, probably even dual fans.
Not sure how easy a Terminator works with an SGE trans controller, if that is important. Might check with them if you are doing an A8.
Terminator does all the standard stuff like SRV and VVT, but might be able to run some kind of a traction control. Something to look into.
Base setup will be easier with OEM, but depending on how far you go, the Terminator might be easier to deal with.
No SKIM on the Terminator. And starter signal setup can be an issue with the OEM controller.
OEM computer probably gets the nod for reliability. Not that I hear of many people having issues with the Terminator.
And a real outlier option, the Terminator probably will never have the option for cruise control. :D Not that I have heard of anyone make the OEM cruise control work. Hotwire Auto sells a kit that works on the stock PCM, but it’s not the PCM that is doing it. Not that many care about CC.