Neither, had both on a 18 yr old car (Flowmaster will always sound good ,but after awhile ,years I mean ,they star to sound like mufflers with or coffee cans with rocks in them ) just my .02 I had what was called the original oval flomaster on a 1983 GT (new ) in 1984 and people freaked over the sound it was so good (2 1/2 back then ) had Flows on 2 other street Mustangs ,85 coupe and a 86 GT all sounded great ,Then I bought my 91 notch and sound changed with there ( then in 93 ) stage 2 ( they lasted on the stang for 4 years ,got the same ,lasted 2 years ) When Magnaflow came out I said I wold try them ,and did .Had a whole exhaust done up with stainless ..Got to say ..they don't have that low noise that flow have ,but when you jump on it !! Everybody ( people i don't no tell me how good the car sounds ? !. I like the Magnaflow sounds. sold.
Tho whenever I hear a tuff mustang (cause I live in Ocean City ,Maryland ) I always love what anybody got ,and sweated to make it BAD !.