I have had both nad they are both awsome mufflers. flow masters have an awsome reputation and so do magnaflows. the mufflers are going to perform different for every aplication and or driver. flowmasters are generally made for the average vehicle to give it perfomance and a good tone and to keep fuel milage up. magnaflows are generally for the engines that like to create there power more in the top end like 4cyl and most newer V8 cars. and for everyones information the magnaflow magnapack is the same as a glass pack exept that it has a different compound of fiberglass packing so it will be quite at idle and Really loud when the led gets put down. in my own opinion everyone should check out pypes, they are like a magnaflow magnaflow but they sound way different, thats what my mustang has on it. oh and pro-stock dragsters use the flowmaster muffler that is a straight through design and not a chambered muffler and there new muffler the hushpower is the same way.
