I'm not familiar with that brand, but in general the longer the kayak the faster it is and the better it will track. If you're going to paddle up stream a lot the 12' is what you want. Of course longer is also heavier to move around on dry land. Shorter is normally more maneuverable, but that isn't a big requirement on our flows. For fishing you want something with a beam in the 30" range, which most yaks I've seen under 14' have.
I prefer a SOT for all but small waters. I have 10' SI that does fine on creeks, but for anything else a 12' SOT is my preference. The SOT is self draining, should be unsinkable and you're able to sit on the side with your legs hanging over to reach the rear compartment. In many, mine for instance, you can store rods inside where they are safe. You can't access them on the move but you can carry spares or a flyrod, for instance, in case conditions get ripe to use it. My tarpon has so so initial stability, but outstanding secondary, which is important for fishing, in my opinion.