The design of the U-boat provides easier entry. U-boats are more streamlined than float tubes, which might provide for less drag and easier travel across the water. Some U-boats can be used with oars, while others have cushioned seats that resemble those found on pontoon boats. U-boat tubes are not standard, and replacements must be obtained from the manufacturer. If you are interested in upgrading from the standard float tube, you are probably better off bypassing the U-boat and looking at a pontoon boat.
Pontoon boats are generally more expensive than float tubes or U-boats.
Compared to float tubes and U-boats, pontoon boats travel across the water more efficiently, and with greater speed. This advantage is due to the fact that you don't sit as far down in the water in a pontoon boat, so there is less drag to overcome. A class-I boat is open at each end, which allows it to glide through the water with minimal friction. Small pontoon boats don't sit up much higher than a float tube, so wind is usually not a problem. These smaller boats may or may not come equipped with oars.