They’re very similar and can be used interchangeably, although their exact composition is a bit different. Both of these contain vitamin A, which can be very harmful or even fatal in excess, though it probably takes a whole lot more than you’d ever give your ferret. Still, some people prefer to dilute them 50/50 with olive oil or vegetable oil (NOT mineral oil), which shouldn’t hurt.
Also, as with hairball remedies, too much Ferretone or Linatone can give your ferrets loose stools. No more than a few drops to one pump a day is recommended, and it’s not thought to be necessary to give them any at all if you’re using a good food. Similarly, many people give their ferrets a small amount of a cat hairball remedy such as Laxatone or Petromalt on a regular basis. This can help them pass the styrofoam, rubber bands, and such that they seem to love to eat, as well as helping to prevent hairballs from fur swallowed during grooming.
Even better, most ferrets seem to think of this as a wonderful treat, too. As with all treats and supplements, give them only in moderation; you can estimate how much by taking the recommended cat dosage and adjusting for a ferret’s smaller weight.