Neil, the big factor in choosing MFI, EFI, or carb might be the your expertise, the cost, availability, and convenience of the professional help you need to get the system working right. Using my situation as an example, I am good with carbs and can do field repair and tuning. No so with the injection systems. Also, I get a discounted hourly rate for dyno work from a shop that has a lot of experience tuning race carbs, not much at EFI mapping, and no experience with MFI. That mirrors my experience, too. The EFI mapping work requires me to pay full rate at another shop and I am at a disadvantage if I have problems in the field.
The decision was easy. It was to go with a system I know and can get good results with vs working with another system I most certainly will have problems with. My son, Josef, is the opposite. He knows EFI real well and carbs are sort of a mystery to him.