MAJOR MAJOR MAJOR Difference.
Counterweights aren’t desined to work the way astrojax are, astrojax use a weight inside of each ball which makes it a lot better. (Except aquas which use inertia from liquid). Also the string for astrojax is a lot different then yoyo string.
Just pick up a pair of plus or v-max if you are curious, they are about 10$ from http://www.usastrojax.com/ Jim (the guy who runs it) is a really good guy and if you have any questions just send him an email.
But if you want to play astrojax please just get some astrojax, in the end you’re only helping yourself because three counterweights on a string are actually a lot different.
I really love Aquas because they are bigger but beware sometimes they leak a bit from trauma. Your best bet is to try some pluses and vmax. Plus are soft foam and VMAX are hard plastic. IF you still like it upgrade to Aquas because they pretty much are the best astrojax.