My Jammin has front Universals, but the center and rear drive shafts are dogbone. I'm thinking about upgrading to universals all around. Is there a significant difference between universals and dogbones?

Thanks.

Yes and No,,
if you just bash around you'll most likely never notice the difference, but having Unis all around will smooth out some of the back lash between braking and acceleration.

It makes the buggy a little smother, a big help if you're racing, especially on a loose track