I had a Borla cat-back system on my 01 Corvette. It sounded great - very low tone. Guys who had a Magnaflow cat back ended up with a sound that was very close, but the Magnaflow mufflers were polished. Both were made of stainless steel with a massive warranty. My Mazda MX5 has a Magnaflow muffler that produces a higher pitch sound than either my old MX6 GT's or son's Honda CX Magnaflow cat-back system, but I attribute the difference to the larger sized muffler and straightened exhaust pipe path of the MX5.
Magnaflow has more applications that Borla but both produce good sound and have excellent quality, IMO.