Well, if you're going to leave your panniers on the bike (and take out your briefcase, clothes, etc and pack them each into work) then yes, they are likely to get stolen. However, since most panniers that I know of can be taken off the rack in less than two seconds most people just leave the stuff inside the pannier and pack it into work. I think most panniers with their soft fabric would actually hold more than a crate. I don't know how much you're planning to haul, but I usually commute with just one pannier... and I have never been able to fill it up to capacity with what I need for the commute and work.