I have stayed in both. Our first trip was in the North wing. We were on the 2nd floor, about 1/2 way down. We had a lovely time. We really enjoyed the wing as it was quiet. We could see the top of the MK and had a GREAT view of the FW's from our window.
Last Sept, we were on the 14th floor. We requested & received a view of the lake. The view was INCREDIBLE. Worth every penny. We went to the concierge lounge to watch the FW & see the MK.
So, when we again stay at the CR, if funds were "tight", I would not hesitate to stay in the wings. I would prefer the tower, but $100 ($700 for a week) is a lot of $$$.
Since you're leaving soon, I think *I'd* wait till I arrived to upgrade. Generally, upgrades upon arrival are less expensive. January is generally a slow month, so unless a big convention is booked, I don't think you'd have a problem. However, if you *really* want a tower, you should change now. Another possibility, is to book a couple of night in the tower, then the rest in a wing room.
Whatever you choose, you'll have a wonderful time! Check out my pic's below. Note, most of the balcony shots were taken with a zoom.