It is the use of the vector brush that gives the smooth lines while in XPro we have the limitation of a bitmap brush. A vector brush is what a few of us have been asking for a while as it restricts many types of users, like people who draw cartoons, portrait artist and as you have shown here graphic design.

Having moan at bit here, on the plus side you would not have to jump from Illy into PS as you could easily dirty up the design all in XPro.