Are you talking about THIS Christmas? I would start checking things out ASAP, as this is a very busy time and it may be hard to get availability. The Disboards are a great resource, but I think you need to decide what you actually want to do! It's obviously a lot cheaper to do DL vs. WDW being on the West, but the experiences are completely different.
I would do a bit of research in terms of what you want to spend, and do on your holiday and then book ASAP. Dining etc. will be near impossible for this week, so you want to decide quick!
Im a DVC member, so we always stay on site... and use West Jet for direct flights out of Calgary. It really all depends on availability, budget and what you envision your holiday to be!