We love Whispering Canyon and all the antics, but I didn't find their breakfast to be anything special. If I had to choose just between the two I'd go with Trails End, just because they have more plentiful and better options (their french toast bread pudding is amazing).
That said I'd also offer you consider The Wave. It is our favorite buffet on property as the prices are low, food delicious, and its much smaller than the other buffets so they food IMO is much fresher. And if you are really looking to splurge California Grill brunch is perfection! Its pricey, but you won't find a better breakfast or brunch on property