A few years before we bought our coach in 2008, the Itasca line cost a little more and offered more items as standard. In most cases, you could add the options to the Winnebago and get the same thing for about the same price. There were subtle differences like arched cabinet doors in one line and straight doors in the other even though which line had the arched doors changed from year to year. As stated earlier, the color schemes are different.
Here in the Tampa FL area, the dealers carry both lines. In other locations, the dealers only have one line to offer.
I would pick the line that has the color scheme that you want or the dealer that you want to work with (if they only offer one line).