I can PERSANOLLY make this comparison. I bought flowmasters at the advise from others.

They cackle at higher rpm's, sound tinny at idle, and TONS of cab noise. THEY SUCK!! Sorry to all you flowmaster guys. JMO
Well I scrapped those in a month and bought the MAGNAFLOWS.
VERY NICE!! Nice low rumble, when you stand on the gas you can hear it ROAR to life, and LESS cab noise.
I am very pleased with the sound and performance of the Magnaflows.