i think it really is your preference...the 4 things i looked for were appearance, sound, performance, and price.
here's a link to most of the exhausts out there, except for maybe dinan. you have to register to see the pics, but if you're serious about buying an exhaust, you should check it out.
personally, i've heard supersprint, acs, and eisenmann's in person. the sound of the acs wasn't throaty/loud enough for me and the supersprint, although it sounds pretty good, didn't look as good as the eisenmann...the acs is a good exhaust, but i don't really care for the figure 8 design...but that's all subjective. i love my eisenmann race exhaust...i think it sounds the best... Go Meisterschaft if you could afford a little more....
get the exhaust that you like...everybody's different. i think quality wise, they're all similar, unless you pay the extra grand and go for titanium exhausts....which are awesome.