Pontoon boats and float tubes are very similar in many respects. They both use heavy duty double liners inflated with air to travel across the water. At first glance, it may not seem like a real decision between them, as they both come in several styles that are comparable, but there are a few major differences. Both pontoon boats and float tubes have their loyal followings and are great devices. Which you pick will depend largely on your personal taste and reasons for using them.
Decide on how many people you want to take with you on your outings on the water. Pontoon boats come in a wide variety of sizes from single-person rowables to full-sized deck boats that can carry parties of people on the water. Float tubes are single-person flotation devices that resemble a swimming pool lounge chair, only much stronger and meant for rivers, ponds, streams and lakes.
Calculate your comfort level. Besides the number of people each can carry, there is a major difference in seating between float tubes and pontoon boats. On a float tube, just like on a swimming pool flotation device, the rider's butt is generally in the water. On a pontoon boat, no matter what size, the seat is aloft over the top of the floats keeping the boater completely off the water surface.
Power, Storage, Transportation
Know your strengths and weaknesses. Larger pontoon boats can be equipped with engines to save the strain on a boater's arms from paddling, but smaller ones can still be self-propelled if desired. Float tubes are propelled by the boater's legs. Swim fins are worn to make kicking more propulsive.
One of the big reasons single boaters enjoy float tubes is that they easily compress and fit into the trunk of a car and can be carried to the water without the use of a trailer. Even the smallest of pontoons, because of the seating structure, require a trailer and are too heavy for one person to carry to the water's edge. If the water you wish to float on is far from a road, a float tube that can be easily carried is by far the better choice.
Consider your finances. Float tubes are very inexpensive. They range in cost from $70 to $200. Pontoon boats range from very inexpensive ($70) to extremely expensive ($100,000 for platform pontoon boats that can hold 20 or more people).