I would actually go with EPS v.8 if that were an option now. I know it's not, but for feature reference that's what I would do. No matter the format, there is always an issue with it from an archival standpoint. Even if you used the native format of the program itself. Features are deprecated or removed (or the program ceases to exist for a variety of reasons), fonts especially are always going to be something that are going to have to go through a destructive process when thinking about archiving for years/decades.
There shouldn't be a difference importing a Mac or Windows base file since Freehand had been in development for both platforms for a long time (since what version 3? and as long as there was feature parity between the two platforms with the native program), it does depend on how good that import driver is just in general though. I would say though, Ai's would be the best as Adobe is the one that had Freehand in the end, so their ability would have been the best (at least in theory), so Corel (or any other program) would not have the best support (Inkscape never had it, and I recall the forums had people that wanted it, but it never happened and some were complaining about the Adobe importing as well). The only thing that would have gone in the other programs favor is that it was killed off, so there wouldn't have been any changes to the format. The only question is, was it worth it for them to keep development for it, probably not. I think Corel's supported importing 7 or 8 in the end, and Freehand, pre Adobe, had what 11 versions in total? So the question is, did they actually improve the import for 7 and/or 8 to the best that they could be or not, I doubt it, but it's possible.
Your best bet is going to be legacy. If wanting to do the Mac route, have to get an older box that runs Mac. Running it via emulation (this is different from a virtual machine (and the difference is key in a situation like this)) would be against the EULA and typically there are caveats with emulators about stability etc due to the EULA. So if you are wanting a smooth experience and you are able to get install discs, best bet is to run an old Mac box and do it that way. On the Windows side, would have the additional option of a VM (I would not go the emulation route for sure in this case and wouldn't need to at that, compared to really old Mac systems at least not yet), but would have to buy an installer for the older Windows OS as well, that may be harder compared to just finding an older Windows box (if you do find this and/or go this route, I would create ISOs of both discs to store digitally (along with any keys), this would make archiving the software far easier compared to dealing with optical media. Just in case a future need arises later on.
