There is no subtle difference between the two - the difference is night and day, black and white. With two engines 20' apart, you can make the boat do a tango through a corkscrew. Strong cross winds are the only thinking one really needs to do because of the extra windage. Our catamaran made me an overnight docking expert.Mark - can you explain the more subtle differences in docking between a two-engine cat and a mono? I have to admit I was never the perfect docker on our mono. We always backed into slips, and ~5% of the time I would be carrying too much speed, or not aligned correctly, or whatever.
It seems you have much more fine control over a cat - both in terms of the engines, but also in terms of dealing with the momentum. Being able to literally spin the boat on a dime, and not have to mess with back-and-fill like on a mono, sounds pretty dreamy.
Our previous monohull was a full-keel, barn door rudder, and undersized prop in an small aperature behind a thick deadwood (a real "blue water boat"). The best I could do with that boat was hang fenders everywhere and keep our liability insurance paid.
All control is done with engines while the wheel is locked in center. It is possible to use the rudders with engines to make the boat go sideways - once you get the hang of it, you can simply exit/enter a dock sideways like you have bow and stern thrusters.