The difference between petroleum Jelly and Vaseline is in the name.
Vaseline is simply just petroleum jelly and is a brand name but Vaseline tends to be more pure than other petroleum jelly brands.
However if you simply need some petroleum jelly and can't afford the Vaseline or want to save money the regular cheaper brands of petroleum jelly will work just as good as Vaseline.
I always used to by the Vaseline but found that the cheaper petroleum jelly works just as good and so now I always buy the cheaper Walmart brands of petroleum jelly and never have any issues with it.
I find no difference in performance of the cheaper petroleum jelly over the Vaseline.