While I don't have Webstorm, IntelliJ IDEA Community Edition consumes 250,000 kb with an empty project open while Netbeans consumes a bit under 400,000 kb, both without any sort of tweaking -- that's not that great of a difference to me. Vim, for instance, would be light.
Have you people even tried VS2010 for js? That thing actually executes your js in real-time so it knows the exact type of variables even after re-assignment and can offer type info/auto-complete that is 100% accurate.