The Ge90 is becoming a very popular engine on the 777 because the GE
powerplant is the only engine that can power the new 773ER/772LR and soon 772LRF variants.
When the 773ER/772LR were being developed, GE
's engine could meet the thrust requirements in the shortest amount of time. Boeing needed to hustle on the project, so GE
took advantage of the situation by offering to cover some of the development cost *if* the GE
engine was the *only* engine allowed on the 773ER/772LR. GE
also had the advantage of being partnered with the leasing firm GECAS, so it worked well for both Boeing and GE
. Boeing agreed that all 777s heavier than 700,000 lbs *must* be powered by the Ge90.
However, the Ge90 is a very heavy engine. On the 772ER, the Ge90-92 and Trent 892 offer the same amount of thrust, but each Trent engine weights almost a ton less. Thus, an airline that chooses the Trent engine can carry that much extra payload, or save on fuel burn.
It all depends on what the airline wants.