I understand, although I can't find the data to back this up, that the Rolls Royce engine is superior on just about every count. Except....it is considerably heavier than the P & W. Perhaps a tonne a side, I doubt that it is two and a half tonne a side to give creedence to the P & W claim of a five tonne payload increase.
The inference here is that the Rolls Royce engine burns less fuel even when hauling along it's own extra lard.
I think the P & W claim whilst perhaps true, is being very selective.
Based on my probably inaccurate hypotheses and fag packet calculations:
If you require an aircraft which flies sectors which require more than 30 tonnes of fuel (ball park 3000nm or more) Get P & Ws.
For anything else use Rolls Royce.