driving to Calgary from Vancouver is it best to go via Kamloops or kelowna. fastest way is the only consideration. Thanks

If fastest route is your choice, I'd drive to Kamloops and then take the Coquilla hwy to Hope and then on to Vancouver.

leuk kind of has it right but backwards, since you are going from Vancouver TO Calgary.
So head west from Vancouver to Hope, then take the Coquihalla to Kamloops and then Highway 1 to Calgary.
I've done the drive in 10.5 hours, including brief stops for gas and meals... in winter it's taken up to 17 depending on conditions.
Going to Kelowna would add time.

Whoops.