You might need to be a little more specific about the intended uses for a definitive answer, but here are some of my observations...
float tubes
- easy to transport, fit into the trunk of a car
- your butt is always in the water, not so nice on cold days
- not efficiant over distance, few yards OK, a hundred yards is a heck of a lot of kicking
- can be impossile to return to launch point in high winds, beach the boat and walk home
- since your legs dangle down you need min. 3-4 feet of water to float
- entering shallow banks is difficult, need to walk in clumsy flippers to deeper water
- legs hanging down can be dangerous in moving water, feet catch and flip ya right over
- light enough that hiking in to remote locations is possible
- not allowed on many rivers do to safety issues
- can't pee out of one, you will need to go to shore and remove your waders
pontoons
- fits in the back of my SUV when dissasembled, or on top when put together
- takes 20 minutes to assemble or take down, prefer to leave it set up for multi-day
- butt sits high and dry in comfy seat with back support, legs can rest out of water too
- low draft, floats in 6" of water, enter or leave shallow water easily
- need flippers or extra set of arms to fish and row at same time
- flipper and oars work best in 'reverse' direction, forward travel is much less efficiant
- big enough for lots of gear, small cooler, live well, spare clothes, 6 pack, whatever
- big wide footprint, really hard to flip one
- some are stable enough for stand up casting, nice feature
- oars provide efficiant propulsion, can also mount small mount small trolling motor
- higher wind profile, tough to keep it where you want it when wind is gusting
- beefy enough for class III rivers, bounces off rocks w/o damage
kayak
- need roof rack for transport, include this in cost analysis, those thule racks aren't cheap
- zero assembly time, gotta love that
- it's a wet ride, you will be sitting in water much of the time
- 90 degree sitting position is uncomfortable for some folks w/ back problems
- paddle and fly rod each need two hands, cannot to fish and steer at same time
- storage space is limited on some models, where do I put the cooler?
- stable but it is still possible to flip them, expensive ones can be fitted w/ outriggers for stand up casting
- very efficiant propulsion, good for long distances or upstream/upwind travel, silent and stealthy
- travel forward, backward and turn on a dime no problem, as long as both hands are free
- might want a paddle leash or spare break down paddle, they don't go far w/o one.
- need full size storage space for off season, 12-16 feet takes up a lot of room
- modern roto molded plastic hulls are almost indistructable, pass boat the along to your grand kids