As everyone has already mentioned you will definitely get where you are going much faster with the Tarpon. It is and will probably be known for a long time as one of the best fishing yaks available so I won't even try to say that it has flaws compared to the Coosa. I can, however, tell you everything you want to know about the Coosa. As for tracking and speed, I have taken my Coosa out on multiple occasions for 5 or more miles round trip and still lived to tell the tale but I'm fairly young and in reasonably good shape. It may take a bit longer but with enough effort I was able to keep up with the guys in the Hobies. They could of course fish while I was paddling but that is another situation all together. The Coosa is definitely an awesome yak though and has versatility on both the rivers and open flats. There are also a lot of well thought out features like the high/low seat, the tackle storage under the seat, the rod and paddle stagers, the low profile flush mount rod holders and the drag chain recess that make it stand out. And as you have probably noticed, the seat is extremely comfortable. But once you get your sea legs you will find yourself standing pretty much all the time that you aren't actually en-route to another fishing hole. With a long enough paddle you can actually just paddle around while standing and get yourself some really good view of the surroundings.
So essentially all I can tell you for now is that if you want to sacrifice a bit of speed on the open flats you can gain a lot of stability and other fisherman friendly comforts. I have heard rumor of the 14' Coosa throughout the forums but nothing from Jackson specifically. Maybe someone can point me to that article or press release. If you wanted a rudder, then you could easily customize an off the shelf rudder system to fit the back of the Coosa. I actually made one from scratch in my machine shop. It works as a rudder but I didn't go as far as to get the foot controls so I don't use it. But to be honest, I haven't really felt that I missed much by not having a rudder.
If you want you can check out my rigging thread on the BCKFC forum and look at all the pics on my photobucket page. They might give you some more insight to your decision. http://www.bckfc.org/showthread.php?303 ... -the-Coosa
Good luck, and I'm sure no matter what kayak you finally decide on you will not regret it.