2 vs 3
The 2000EX and 900EX have almost the same airframe, and if we compare a 1000NM leg, the trip fuel, for the 2000 is 3915 lb vs 4150 lb in the 900. I would guss that most of the more fuel required by the 900, is because of the 2000 lb higher BOW.
Runway required for this leg would be 3370ft (2000) and 2795 (900).