It'll be quite a drive and the costs not might be worth it.
But I can say the conditions at Sunshine have be fantastic so far this year. Lake Louise has also been good, but find that Louise tends to get packed out and icy pretty quickly. Paradise bowls are usually fine as the trail markings tend to scare a lot of people from that area. If you're coming this way I'd hit both areas. Sunshine has more consistent snow as the resort is higher up in elevation.
We've been to both resorts for the past few weekends, both resorts literally got dumped on this past weekend for snow. I believe Lake Louise got 16cms Friday night and can say Saturday was some of the best conditions I've even skied in at Louise. Paradise and Larch chairs were great as they are on the backside and less busy. Top of the world had some great snow, a bit windswept at the very top. Being + temps on the Celsius side didn't hurt either. Sunshine was also great all over the mountain....we preferred to lap Goat's Eye, Divide and Standish chairs.
Ski conditions in both Banff and Jasper have been great this year. If you do make the drive, I'm certain the conditions will be worth it compared to the conditions you have in Whistler right now. However it is a big cost for time (driving will be fine as the roads are good right now....should be less than 10 hours), accommodations and lift tickets. With a week left in your trip only you can factor the cost benefit.
However if you are the coast, perhaps Big White, Fernie, or something closer has good conditions as well? I know Fernie doesn't quite have the base they normally do, but it often pukes snow from time to time.....it also has been raining though.
If you do head to Lake Louise and Sunshine, Costco has discounted lift passes for both resorts; off the top of my head it works out to about 25-30% off the daily adult rate. Louise comes in packs of 2 and Sunshine in packs of 3. All separate passes and not consecutive days.
Just a couple sense from an Alberta local.