More players roll imperial side. Thus, more noobs, FTP, and/or inexperienced players w/bad gear VS. pubs who are often long time vets on their geared alts.
And for some reason, pubs usually have more healers while imps often don't have any. This goes for lvl 50 wz's as well.
^^^^^...This. I'm leveling my first pub now and have thoroughly enjoyed the fact we have less players and are always fighting imp teams. I have no idea what everyone is talking about gear though. It's fairly simple for any noob to spend wz comms on the standard pvp gear from the vendors. There's no real secret to it.