The big difference, from a skipper's perspective, is the finesse you have to use bringing a big mono to the dock vs. a cat. With a cat you have positive control all the time and can totally control the situation. It almost doesn't matter which way the wind is blowing. With a mono the wind can flip your bow around and you will not be able to overpower the wind with the engine. You're going around whether you want to or not. Same thing picking up a mooring. So... you really need experience reading the situation to bring a big mono into the dock professionally and safely. Some docks are easier than others, of course. The worst is backing down into an inside slip with the wind. You'll have to pull all of your tricks out of the bag doing that.