Just flew 889 and 888 recently.
As a 1cl pax, you can enjoy the pre-flight dinner service in the BA Galleries Lounge at JFK, which I enjoy more than the BA 1cl lounge.
One thing to keep in mind, on 889 you stay on the plane and the cabin will be cleaned, which can disturb sleep if you're seeking to sleep. JFK to YVR 1cl meal service has been cut back from years past; fewer menu choices, quality seems a bit lower and no caviar. Cabin staff however, is as good as ever and they admitted embarrassment at the food quality.
Full dinner with more and better choices is served out of YVR, but it is pretty late at that point.
Returning, I had strong tailwinds so we arrived YVR an hour early, which made the layover extra grinding. Once upon a time one could roam around a bit of the airport terminal; today, you're confined to the gate which is pretty bleak. They should set up a mini-premium class lounge within the gate area.
But, as a 1cl passenger you'll be the first in line for the security screening. Y passengers get to enjoy a long queue.
Those same strong tailwinds also resulted in a half hour early arrival at JFK. Hopes for a quick exit from the airport were dashed as customs/immigration staff do not report to work until 6:00, and I think it was the first day of some new ground staff who had difficulty docking the jetbridge--we could not alight until 6:15.
I'd rather the captain just fly a bit slower so that we can enjoy the 1cl cabin a bit more than the YVR lounge or the sitting on the JFK tarmac.