The only thing that determines which way the drum spins is which side of the sail has the UV stripe. Since your sail does not have this stripe yet, you are free to choose. Just make sure you tell the sailmaker the correct side!
After that, it is a matter of choice which side of the boat you want the furler line to be on. One side might be more convenient than the other for reasons of an additional winch/cleat/clutch there, or something is mounted in the way on the other side (you don't want the possibility of putting your knee through your engine panel, for example), or that you are naturally stronger and more balanced pulling from one side than the other.
Once you've chosen the side of the boat for the furling line, then you can still have the furler turn in either direction by leading the line off the fore or aft end of the drum.
There is one school of thought that the drum should furl in the direction the forestay wire lay turns. This is so that if something binds under the load of furling, it doesn't try to unlay the forestay. Also, if you have a mechanical fitting, the drum doesn't try to unscrew that if something binds. Personally, I don't think this is much of a risk.
Otherwise, I've never seen a drum that can only furl in one direction, although I think there is one furler out there with a locking pawl, and that might require a particular direction. For sure, the Coriolis effect has no practical effect on ease of furling, if it is measurable at all.
The best way to furl a headsail is to turn downwind. Port/starboard has little bearing then, and isn't really an issue unless one is always furling in a fleet of boats under sail close to them. Even then, it really isn't an issue.
You are free to choose.
Mark