http://www.fragworld.org/frag/community-blogs/brink-info-pt-3-weapons-and-customization.html
Resistance and Security can both use the same weapons, but the weapons look and sound different when they are held by the different factions.
"?- Although gameplay-wise, the weapons are identical for each faction, they will look and sound different for each. Security weapons will look and sound pristine and well-maintained, while Resistance weapons will look and sound begged, borrowed and stolen. In addition, there is also separate audio for hip firing and when you are aiming down the sights for weapons, since you are closer/further from the chamber/trigger mechanism." - HORSE
Also, you can see the Ceaser Revolver being used by security in the Choir of Guns Trailer
http://www.youtube.com/watch?v=tI4y2P0r7K0
At 19 seconds in. 0:19
On average I would say that the Psycho Pack seems to be angled more towards Resistance than Security, simply because clothes seem to be one of the few things that are faction specific, and the Grin mask looks like a Resistance only thing. However, the Revolver and Silencers are both neutral, since they both seem to have appearances for both factions.