I personally feel its better to separate them.
I work in an environment where things like action names or pages are a like between the 2 platforms and can be exactly the same so it makes it more challenging if you want to report then you need segments. Imagine in report builder then you need to have extra segments vs just picking each reportlet and pickup just report suite.
Also if one env suddenly pollutes data then both platforms get hit.
From Adobes perspective there is no extra cost in setting up 2 report suites vs 1 as it boils down to server calls.
The main difference between having two report suites is you double your server calls and you lose the ability to track all of your customers/users if they are across multiple devices. We learned the hard way that we wanted everyone in the same report suite, but it really comes down to your business case. I have worked with a very large business who has asked us to use a VRS for reporting, and we also work with a third-party contractor (Evolytics) who also has experience working in the VRS environment. The entire reason for the Virtual Report Suite is to reduce the cost behind multiple/duplicate server calls, but again, this is something you must decide, based upon your specific use case.
Best of luck!