Not sure what you mean about the set up. OR is an open source near copy of Rocksim with maybe a prettier interface, but they are nearly identical to use.
It is just as easy to upscale in RS.
I like RS better because I can model tip fins and tube fins. RS seems to be more accurate in terms of altitude with different fin edges. RS has been around quite a lot longer and is a finished commercial product with tons of support. Apogee has dozens upon dozens of documents on their website on how to do just about anything you want! With OR you have to ask the community and hope something is possible. Though OR can also open RS .rkt files, they don't always work right.
I will give OR an A+ fr presentation. It's purdy!
Jerome