Does it offer any advantage vs energy weapon over combat armor?

No

Metal armor is only good for one thing; repairing Power armors with Jury Rigging.

There's an associated perk that comes with Dead Money that gives DT against laser weapons when you wear metal armor and glasses.

Unfortunately, the few energy weapons you'll actually face are in the hands of the Fiends, who die like Bloatflies to any decently built character, so you probably won't get much mileage out of this perk.

Then again, I rarely, if ever, take such specialized perks and do not make a habit of regularly clearing the South Vegas Ruins, so if that's your thing it might prove worthwhile.