DD19 and I just returned (12-19 Jan 2008). We played Fantasia, Winter AND Summer! Not on the same day, though. We've been playing the Fantasia course for several years and have been disappointed with the upkeep (or lack of upkeep). We really enjoyed the Winter course out of all that we played this time.
She did mention that she wanted to try the course that is next to Fantasia (looks more like a "real" course) on our next trip.
I'm not sure that you can say that one is more challenging than the other. I think they are just meant for fun!
BTW, if you play one course and save your receipt and play another course the following day, you will receive a discount! We read a sign next to the cash register. We inquired about it, but since we are AP holders, we had already received the same discount.
Have fun!