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Oh, The GE engine uses 5% less fuel than the RR - that probably swayed it.[QUOUTE]
That is incorrect. Earlier models of the 787 monitored with competing engines were seeing up to a 2% better fuel performance with the GE's. However now its probably closer to 0.5% in better average fuel burn on the GE's.
The GE's give a better performance during cruise and as common with RR engines they give a much better performance during take-off, climb and descent stages of flight. So I guess if you're planning on flying the longest sectors of this aircrafts capability, cruise performance might be a higher priority...