I personally have not been to Whistler so I can’t give a totally detailed comparison, but in passing I have heard Whistler compared to Disneyland, whereas Fernie is a true working town. If the ski hill weren’t here, Fernie would still exist, which gives it kind of a unique twist. The cost of living is very reasonable. You should easily find a room for $400 for the winter, the earlier you come and the longer you commit to a place, the better for you price-wise. Groceries are not cheap but they certainly can’t be more expensive than the coast! A pass is cheap if you work at the hill, otherwise, it’s pricey but you’ll get many many days in since the weekdays are not busy at all – it’s great for those working weekends.
Fernie is a great place to live and work, I think you’ll find it a positive move. If you’re looking for lots of services and chain stores like The Gap, it’s the wrong place, but otherwise it’s great!