fully agree with ferracci: go with what YOU want. same as modifying a car or remodeling a home: how do YOU want it to look.
as for slip-on vs. full, depends on what you want. supposedly, the slip-ons don't do much for power and change bottom end and mid-range a little, but not too much. they are mostly for sound. the full systems are for even more sound but mostly power. downside of an aftermarket system is that yeah, you gain power, but usually only in the upper-rpm range. the advantage of a stock system is that they are tuned for the entire rev-range and they are smooth throughout. if you race or ride at high speed, the full may be of advantage for you. i will say that the best exhaust i ever heard was a full yosh system with pcIIIr on a gixxer 1000. that bike sounded frightening.
as for sounds, i don't care for muzzy on kawi's although they used to be the racing exhaust for team kawasaki and he is one hell of a tuner. to me, they sound like a raspy lawn mower. if you want a shredding type sound, muzzy is it. d & d is close to the muzzy in sound, but a little deeper. micron and two brothers sound nice and deep but louder than stock. team kawasaki rides with akropovic now which is supposedly the best exhaust available. it's pricey, but they offer the best results for power.
again, it's all up to you and what you want. hopefully you'll get some good feedback from others as to what different exhausts sound like.