What is better the flowmaster 40 series or flowmaster 50?

I drive a 2004 jeep grand cherokee. I want loud but i also want it to be high quality.|||Like previous answer said 40 is louder if u want quality get it in stainless steel|||I'm not sure of the numbers, but tell the muffler shop you want the medium flowmaster. That is what they recommended to me when I get it.|||The 40 is louder than the 50.