The RR engine is not so sensitive...
In fact from idle, it needs quite a nudge to increase the N1, the first 2-3mm would make very small difference (you don't even see the fuel flow increases).
As for merits of the RR, it is a great engine to fly but most RR engine failures so far have been associated with the gearbox and accesories. Have not heard any trouble on the GE so far.
Was also told that the GE weights about 8000lbs more than RR, so a higher zfw. But it burns less fuel than RR !
Hope this helps.