Not sure what RBR did with Webber was terribly smart.
I mean, it's okay to say that he'll be starting on the more durable tyre but, at the end of the day, he's still got to run the option tyre as well.
Drivers starting on the options will pit early, while the cars are all quite close together on track, and be able to chase them down quite quickly whereas those who start on the primes and pit later, once the field is more strung out, won't be able to catch and pass the field as quickly.