I researched the gibson catback and if i remember correctly reviews of it all said it was a pretty quiet muffler. The only problem i had with my flowmaster catback other than it rusting away was that it`s tough to get the tails to hang evenly and it drove me crazy. They also hung low and i wasn`t a fan of that either. I can`t say for sure other brands will have the same issues.
The big reason i had one custom built is that it`s all welded and as you saw in the picture i posted the tails are even and tight to the body. And above all stainless.
If you decide to go the custom route and you can`t find a shop up by you that can do it you`re only around 60 miles from the place i got mine done.
http://www.kcscustomexhaust.com/