Merlin is larger (15t) and has 3 engines, 5 blades. External lift ~ 5,000kg.
MRH/NH-90 is smaller in the ~10t class (ie. blackhawk, big-puma). Only 2 engines, 4 blades. External lift ~ 4,000kg
They both look similar due to the rear ramps. An ATV can roll off the back of the NH-90 (
link).
Both helicopters use the same engines.
You could say the NH-90 is more Euro than Anglo. Also, lots of commonality with the (ARH) Tiger gunship.
EUROCOPTER (France/Germany) 62.50%, AGUSTA (Italy) 32.00%, STORK FOKKER Aerospace B.V. (The Netherlands) 5.50%.
MRH-90 vs. BH purchase? see:
link