I've found that they run truer, less wear and tear on the chain/bar/saw and cut a little better/faster. I use Stihl PS3 chains on them. There seems to be less friction for the saw to overcome, and you can usually find a kit for a lot of the more popular, highend saws. These usually replace the clutch drum with an Oregon one, and you'll be upgrading the stock paddle wheel sprocket to a rim drive system. More efficient.
Downside to the PS3 chain is that it isn't anti-kickback type, it's very narrow and made for highspeed cutting, so you'll have to be more careful about kickback if you go that route. Not a big concern, if you're already careful about this. The anti-kickback chains are largely a response to homeowners constantly hurting themselves, because so many of them think that if they can get the saw started, they instantly become manly lumberjacks who scoff at safety precautions and use 40-foot Walmart aluminum ladders for tree work.