Round vs. U-shape
I own both shapes of belly boats, and I personally prefer the round......
here's why: With the round boat, you can rest your elbow on the front and let it hinge comfortably during your casts, also it serves as a rest when I'm working up a fly. The best thing about my U boat is the enterance and exit of the water....but that's all I like about it. My back starts to ache after about 3 - 4 hours from not having a 'good' front rest. I'm afraid these round tubes are going to go extinct at some point. I hope to build a supply up before they do. Of course.... this is all just my opinion. Obviously, there are a lot of people out there who prefer the U as shown by the great number of them on the market. Tough enterance and exiting is worth it to me in order to have hours of comfort.