As far as fuel efficiency goes, the -R Pratts aren't even close to the GE's. Typically close to 1000 PPH higher per engine than the GE's, at least for the first half of the flight. They get a bit better the lighter you get.
Do like the extra oomph from the 'R's. MGTOW of 833K # with the GE's your pretty much wheezing @ TOC / FL290 when it's hot. The -R Pratts just march right on up to cruise altitude, no worries 'mate.
The Pratts are also good entertainment, watching FO's deal with the greater idle thrust on arrival and approach. It is always fun watching them run with the engines unbalanced, thinking that all four thrust levers matched up will give them symmetrical thrust. With the AP on, in level flight, and the yoke is displaced significantly to the right or left, I would love asking the question "does this look OK to you?". Ah, a learning experience!
For real efficiency you should see the fuel flows on the GE90-110B