It is all about aerodynamics, the exhaust of the third engine and the design of the tail section induce a laminar flow with virtually no parasite drag. The work on the Falcon 2000 for the computation of the area_ruling that governs the aft fuselage was horrendous.
Therefore, with the the same amount of thrust you are saving around 30%, just in aerodynamic excellence. On a Falcon you do not have unnecessary feathers.
Now a cabin size stand point , the 7X could have been better, but since the fuselage certification is a big chunk in a program; Dassault is still using the grand fathers rights of the Falcon 20 certification....only 40 years old...bugg_er.
Now they want to go all electrics...a twin-engine electric...;sounds like a R/C model...
