Not sure about the nature of your question.

My experience would suggest Ottawa, but YOW also has fewer transborder CBP officers, so if your question is about wait times it's probably moot.

Also, 'number of aircraft' is a bit of a red-herring - There will be considerably more bodies in five 757s than there will be in five Dash-8s - The same number of aircraft, but way more pax.

As to VIP service, it varies by airport. In Vancouver, you go through security first, then talk to CBP. If you have nexus they in theory move you to a faster security line, but I don't seem much speed as they also put Kettles with kids and wheelchairs in that line.

In Toronto, you go through CBP first, then security. Nexus will get you thorugh CBP faster, and then if you're an elite you can go through a faster security line.