I would like to create two programs that reference the same email creative. What is the best way to do this? Would it make sense to create the email creative in the Design Studio in the Global Email Folder, and reference this from Marketing Activities?
As per your convenience you can create email asset to reside either in Design Studio' Global folder or under Marketing Assets directrix.
If your program structure is likely to be re-used you can create a program template with tokens. With each of the similar program build requests to send out emails you can customize as per the need by making the updates at token level instead of editing email assets.