Well I have a quick question for those who are familiar with either of these apps

I own a low end version of acid that I do not really use at all since it was some what of a freebie of sorts, called Acid DJ, was a 30 dollar app, and doesnt do a whole lot aside from let you loop 8 seperate tracks.
Now, a while back I entered a remix contest and won a whole mess of sony apps as the grand prize, one of those prises was the blue box version of Sony Vegas 5 + DvD, but here is where I need the help.
I am interested in using Acid for some loop edits, I run Nuendo as my host but I realize that Acid is the best tool for loops, so what I am wondering is..
If I own Vegas 5 is there any reason to use Acid? dont these apps basically do the exact same thing but vegas is the considered their pro end version for audio/video?
In simple form, is it worth it to buy Acid Pro if I already own Vegas 5?
To be completely honest since I have won Vegas I have yet to install the app since I was considering of getting rid of it to get more needed gear but now that I am considering Acid as a possible loop solution, would it be worth while to keep Vegas instead of using Acid as I had asked.
Thanks in advance,
Cheers!