I have not had an ERA
but I have had inboard jag set up on a CCX. Servicing was easy as the calipers I used were the type with the pin at the top that held in the pads. Remove the wheel and a brake pad change was minutes, however changing discs took about an hour per side. That said, choose the right caliper and inboard are fine for these cars.
If $ is no object, go for the outboard. Why? Well why not......