i have been trying to find some research on both here and google and no luck. ino both of them help out on handling and suspension but i was just wondering, do they serve the same purpose bc i know that the upper strut connects on the inside of the rear, behind the seats and the sway bar is underneath the car, but could you use both of them or would the be pointless? if u would have to choose between the two wat one would it be?

 

That rear strut bar doesn't help. Just because it connects the rear side or any part of the car doesn't mean it's beneficial. If you look at the back where the two strut rear towers is, it's already connected and supported by the chassis of the car so having another bar connecting to the two rear struts probably doesn't do anything.

The sway bar on the other hand will do something towards the handling. The stiffer the rear sway is, the more body roll is reduced (although having too thick of a sway bar may not be beneficial either).

 

Get a rear sway bar. You'll feel the improvement a lot more than a strut bar.