Right side driveshaft normal or fat version??

I've bought some used driveshafts for a DX engine upgrade. The seller sent me two versions of the right side, one I believe is the original from a dx engine and one from a later cabrio that has a fatter shaft. Does anyone know if the fatter one has any advantage and/or why it's fatter??

Thanks for any input

The early 90mm axles were thinner than the 100mm axles, but I have never seen one that fat on a OEM Rabbit/Golf or Cabriolet.  

The 100mm axles were beefier as to the HP gains of the
engine over the years, but I have never seen one that Beefie…. Better or worse?  all depends on the quality of the CV ends that are being used.

45hp 1.5 Diesels don't need a axle that is rated for the higher hp gains of the 2h engines IMHO.

Shoot I am probably a rare bird as I had gotten over 330K on OEM axles, but I did take care of them…right before I sold my Diesel I was debating about changing them as they did start to Groan on turns after a stop for about the last 30 K of ownership.

I have a standard DX engined 83 GTI and it has a fat RH drive shaft like that. Not sure if that helps you much or not, I can't remember what size the inner joints - 90 or 100, but I can measure them to confirm.