When I did my theater originally (4 years ago) I did hard tubing as well. One 90 degree bend in an almost full conduit can ruin your day fast.
If it bends, use the flex stuff, if it's straight, the rigid is cheaper and better. When in doubt, go a size larger or run an extra conduit alongside.
And the best piece of advice I can give: leave an extra pull string (Cat5 or phone cord works best -- don't want something flammable in there) in your conduit. It makes pulling an extra cable a few months later MUCH easier.