So i read most of comments and didnt find an answered i liked, so i im going to throw my 2 cents in.
For pve, i believe the gunnery commmando will do more consistent dps with gunnery spec because a vanguard playing assault spec will be at a small mercy of a little thing called RNG with ionic accelerator procs, if you get those procs your dps has POTENTIAL to be higher than commando.
For pvp vanguard wins by miles because it is so hard to lock these guys down and they are so durable. For a commando i can lock you down so easy as vanguard I can riot>cyro>riot>neuroshock>riot>move a little and pull, usually fights end around 2nd riot or neuroshock if commando isnt getting heals