I was waiting for others to weigh in. ESD is something of a religion, and I hate to wade into that territory.
Peronally, with my limited experience in machining stuff, I would for sure use aluminum. If ESD turns out to not be a problem, then you're set. If it does, then you will have to do some more hard work to figure out what to use.
In terms of rigidity, weight, durability, and DEBURRING (or lack thereof of aluminum vs plastic), you will have a hard time to beat aluminum.
I am not going to weigh in heavily on ESD this or that, but I store CMOS stuff in brass tubes for several years, now, without any problem. The brass tarnishes, but it's not as tough a coating as aluminum oxide. Still I bet it's enough to prevent an electrical contact for the tiny SMD components resting in the tubes. I don't believe aluminum is known to be particularly triboelectric with other common materials in way that you could, say, build significant charge on glass by rubbing it with wool (which I say as just an example from memory which may be completely incorrect, but you get the idea).