We put a c-18 in a claas 492, runs killer. The only trouble we have had was a couple of injector issues through the years. This is a tier 3 motor though.
It sounds like you are choosing krone, and just deciding on power plant. We ran the new cat powered machine and it is great. Power curve is sweet, cruise using constant power works very efficiently in this machine. I was really impressed with it. Much better than the 1000 we had, and constant power was ok once we played with parameters enough. The c-18 is very smooth in that machine.
The big problem is fuel consumption. Because of all the emission controls that thing is THIRSTY! I am not sure on total gallons on board but starting at 7 and by 3-4 o'clock it was time to look for the fuel wagon. That was running an 8 row head. If you could get the motor reflashed to remove all the garbage you would have a sweet ride.
The man motors were very good on fuel but the torque curve drops off like any other v motor, but not as bad. They pull hard. The 980 is hard to get full enough sometimes and thats at 884 ish hp if I remeber right. If I am not mistaken all of the man engines are over the horsepower rating for them to need to be tier 4. Which to me makes this an easy choice.