I am also a lover of fast groomers and I would send you to Copper over Winter Park in a heartbeat! To my mind; Winter Park skis with a 'broken' feel, while Copper is one of the more logical ski areas in Colorado. They are both good ski areas, but Copper has an edge that only comes with terrain to complement the infrastructure.
Understanding your financial restrictions, and also understanding that a person seldom wishes to ski the same area for four weeks straight; I would reccomend that you look into the Ski New Mexico pass to complement whichever season pass you get in Colorado. If you have transportation, the pass is very inexpensive. For $195US you get two days skiing at each of the ski areas in New Mexico. New Mexico's ski areas are about the size of many of New Zealand's ski areas, but are quite high in elevation, so you often get quality snow conditions during the dead of winter. The drive from Copper to the New Mexico ski areas is an easy one and can be done almost entirely on interstate highways. There are 7 New Mexico ski areas, and the pass gives you 2 days at each ski area; so you get 14 days of skiing at a little over $13US per day. Mix this in with the least expensive ski pass you can find in Colorado; and I think you just might wind up with a vacation to remember!!
Check out the New Mexico sampler at www.skinewmexico.com.
Feel free to ask further questions about cutting trip costs as time goes on. Many of the forum members really enjoy lending a helping hand to foreign visitors.