The big difference is whether or not they will stick between beers.
With perlicks, you can go a couple days between pours, and they won't stick at all. With standard faucets (unless you're religious about cleaning the faucets after each pour) will typically stick after sitting for a day or 2 without being used. I used to have standard faucets, and had one stick so bad that a friend of mine actually broke the internal lever on the faucet trying to get it unstuck. I've heard of this happening to a few others as well. Basically, if you've got the money, spend it on the perlicks.