It will come w/ a Rollomatic ES from the factory. Keep a very sharp RS chain on it and keep it oiling right, and you won't have to worry about a replacement for it for a while.
I like the very aggressive large-diameter-nose (3003-000-9622 on my 044) Stihl RS bar, and I wouldn't even look at any of the other makes if they didn't have an oil dam behind the inlet.