If you will always need to use the wheels then I would just go for a wheeled bag, personally, to avoid the hassle of dealing with a separate cart. I was trying to think of an advantage to a cart setup and the only things I could come up with were (a) you could possibly get away with not gate checking on regionals (but you might have to carry the bag past the GA?) and (b) you would probably get more packing capacity using this setup in comparison with a wheeled bag of the same dimensions. It's a personal thing but neither of those considerations would be enough to bring me around to this option.

HTH