Which is better? I have a '91 TT with chip, intake and exhaust. I'll be installing a lightweight flywheel, downpipes and most likely an underdrive pulley very soon. To my understanding the main benefit of the 1 piece assembly is the removal of the main support bearing and a 'u' joint. Obviously weight reduction is also a benefit, but I wouldn't think that weight makes as much difference here as it would on the flywheel since there is less rotational mass on the driveshaft. I'm assuming the aluminum shaft is lighter, but less durable and the gains made from the aluminum shaft would be negligible over the steel shaft. Am I on the right page, or am I way off?

 

Agreed. The difference in weights from the Aluminum to the Steel is negligible. Unless the difference is greater than about 10 lbs, I'd just go with the less expensive steel.
Carbon Fiber is also available for a material to make driveshafts. These are only for the die hard because they're about 5 times the price of steel.

 

If you got an aluminum driveshaft, Can I ask where you purchased it from and for how much?