Long tube normally yields more bottom end..longer tube headers allow for more scavanging effect and burns off the fuel in the collectors..which produces more lower end TQ......
Then you get into back pressure thing,,,which i do not know enough about to give adviseon..all the stauff i ever ran needs to get the exhaust out..not restrict...
long tube is my vote..
__________________
Bjuice..
"I'M YOUR HUCKLEBERRY ! "