They're actually shit.
It's not even about emo this or that, if we want to get technical. I think genre labelling besides the obvious (Rock/Metal etc) is stupid.
I have three genres. Bands I like to different degrees, bands I love to different degrees and bands I hate to different degrees.
I don't see the point in all these different "cores". Metal"core", Grind"core", Rap"core", Emo"core".
Brand New fall into the latter. They're also a shit band, gives it that extra umph.
Whilst emo might get unfairly and improperly stereo typed, if someone says they like emo, I can usually name about 14 bands who they will like. None of them sound different.
-AC