I have driven both and prefer the 413. It feels better to me, but I can't give you numbers to explain why. Seat of the pants calibration is a personalI have to add a second to Kenyon's impression of the 413. In my experience, the 413 is a much smoother engine than the 440. I've driven a BUNCH of cars with both, and while the 440 may offer a bit more power, in an Imperial, I prefer the smooth performance of the 413.
thing.