1/4 vs 1/2 inch exhaust pipes?

[big T]

I am currently running a 21/2 in xpipe (minus 2 rear cats) to spin (Prostreet) mufflers out the stock pipes. A friend told me that he did the same thing, but used 2 1/4 pipes all the way to the tailpipes. Which is better? His sounds pretty good too. I have a 02 gt auto/he has a 01 auto.

 

[DBMSTNG]

2 1/2" is the better way to go.

 

[JoeySperz]

2.5"...Less back pressure/better flowing. Thats the whole reason for changing your Exhaust.