I have a Tarpon 120, and I really like it. It paddles and tracks great under most conditions. The main drawback is that paddling efficiency goes way down in rough water conditions relative to some other kayaks.

I would say that if your main use is really going to be warm water streams and creeks, maneuverability is an important attribute. 12' is a good all around size for versatility. But shorter 'yaks will do better on streams and creeks because they are easier to turn. Of course, you probably know that already because you've researched it.

The LL Manta 12 has a higher profile than the Tarpon 120. You're going to have a drier ride but you'll catch more wind. Maybe wind isn't an issue if you're always paddling down a creek.

Good luck.