If you REALLY want the space, use the CR1s! Always!

Even if it is your experience that an upgrade *always* clears on a route, irregular operations can mess you up.

On the LAX-HNL route, I have missed an upgrade with e500s once because of a earlier cancellation. I have also been confirmed on a CR1 and the plane downgraded from a 767 to a 757. Many people did not get their upgrade that day but I kept mine!