I prefer to do that outside of Premiere and use http://www.scootersoftware.com/moreinfo.php?zz=moreinfo_compare
It allows me to compare the contents of different directories on different drives or computers, even over a network or VPN and copy left to right, right to left or synchronize left and right. For me that is far easier.
Example, I have CS5.5 installed with various plug-ins. Now I install CS6 and want to continue using the same plug-ins. I then use BeyondCompare to find the missing plug-ins in the fresh CS6 installation and copy from CS5.5 to CS6 those missing plug-ins. That makes all those plug-ins available in CS6 as well, instead of reinstalling them again for CS6 only and entering my license keys for all of them. Much faster and easier.
Another example. I have a lot of audio tracks on my old system and I don't want them on the server, but do want them on my new system, so I use synchronize to keep them in sync. We are talking about more than 100 GB of material. In just a few clicks both machines are synchronized and it has the side effect of being a nice backup. Now I add a new album to machine A and synchronize with machine B, job done. Material is available on both machines.