Really depends on what your doing with it. Drag racing "generally" uses the heavier steel flywheel to help maintain engine momentum on the launch. circle track or road racing "generally" uses the lightweight aluminum to help with acceleration out of the corner. Since you mentioned "off the line" I'm assuming drag racing and would recomend the steel. Be sure to get an SFI spec one. Or once your car gets fast and the tech guys start looking at it hard you will have to buy one any ways. An sfi clutch can is in order too Even for the street. I had a clutch explode in my Camaro once, went right through the stock bellhousing and I felt it hit the trans tunnel next to my foot
almost pulled a Garllits!