Thanks for the link, Tasha.
Sorry, I don't have any experience with Wysong, but I really like the Innova food, even though I sometimes have difficulty getting it here, since it is often held up at customs, and German suppliers frequently run out. Supply problems due to inclement weather, for instance, are one reason why it might not be a bad idea for you to alternate Innova and Wysong, provided they like the latter and it agrees with them. Another reason is that it is very difficult to get cats to eat prescription diets once they've gotten used to only eating "their" particular brand. If they're accustomed to some variety, they're more likely to agree to eat something new.