Just look at the stats.
Commando bren stats weren't touched by the latest patch.
Commando brens are insanely strong.
Commandos with double brens are insanely strong at max range because they have, as vipper pointed out, similar dps to obers even considering the fact that the stens basically do nothing at that range.
To that end, commandos with brens have similar dps to obers at max, but the commandos lose dps slower with model loss than obers do.
Vet bonuses are generally in obers' favor. Good to note though that commandos get the ambush bonus with vet.
Commandos with brens are pretty nicely priced compared to other similarly performing infantry. Vipper already compared them to obers, but you can also compare them to double lmg paras, which perform worse than commandos. 380 mp (if im not mistaken) and 120 muni for a squad thats less durable than commandos (6 models at target size 1.0) and has less max DPS.
It's worth noting that paras are much cheaper to reinforce (28 vs. 35 IIRC). They also have an extra man and the ability that lets them suppress with 1919s.