Hard to argue against Flows, they are so popular and are widely acknowleged by community members.
Buuuut...
I for one don;t want to sound like ~30% of the cars and trucks at the local staurday night parking lot. I also don;t really care for that metalic sound that so many others like. I don;t mind them being loud at WOT but I kind of like them mello at idle. I also prefer the tones to be as low (pitch not volume) as possible.
I chose magnaflows for mine based on sound clips I've heard, but be carefull using sound clips to decide. There are so many folks who have recorded their own cars that two identical setups can sound different on the WAV/MP3 file, this is based on the recording techniques and hardware as much as anything. I found a site once and lost the bookmark where they tested many popular mufflers on the same car on the same rack with the same technique. I'll see if I can google for it.