I'd say it really depends. Lux typically has stronger pushing power, but Brand should be decently able to hold his own.
Brand is not as good at roaming either. He is certainly able to do it, but his "gank" ability (his stun) requires more set up.
Lux can stun, deal an AOE of burst damage, assist the laners by shielding them, or just pop off an ult without even entering the lane and assist other lanes.
As far as what brand WAS doing, .. there isn't any way for me to really know that. (at least not until we finally get the replay system). One thing he should have been doing is pinging MIA, pushing the lane, or at least taking chickens. (that may sound like a joke, but getting himself fed during the laning phase will make him much more valuable when team fighting starts)
Now, I'm assuming that you lost, or you probably wouldn't be complaining, so I'm assuming that he didn't do these things, or there was some other failures on your team and/or good plays on the enemy team that ultimately led to a loss.