I happen to almost have both of those models and I prefer the Super Fat Cat. Although they are both awesome and I got a really great deal on my Fish Cat and the Super Fat was a lot more money.
Here they are:
Regular Fish Cat perfect for Wife. 189.00 at SW
Here's Super Fat 400 and something a few years back. I like the inflatable seat but dont like inflating it. It packs up quite a bit better.
Cant go wrong either way, if you have the coin with no issue go with the Super.