The F series Taylorcrafts are not quite as light/nimble/sportscar as the B series Taylorcrafts. This is because the engine is 4 inches more forward, and the baggage compartment is certified to hold a lot of weight. So the mass extends further each way from the balance point.
The T-craft will go about 20% further on the same amount of gas due to lower drag and higher cruise speed. Although very minor, it is generally agreed by the high-timers that the Cub will take off and land a little shorter. There are very few places you can go in a Cub and not in an equal HP T-craft.
Side by side seating can be a major advantage to some, and less desirable to others. That should be a fairly important consideration, based on YOUR preference or mission, or passenger comfort.
I've owned a J-3 and a few T-crafts, and they are both inconvenient to get in and out of. The back seat of the J-3 was not as much of a problem, but in a PA-18 I believe you're going to be getting into the front. Getting in and out of the front of a J-3 or PA-18 was much more annoying for me personally than the T-craft, but I'm sure others might feel the opposite way. The point is that you should definitely try both of them prior to your purchase.
As Courierguy said, do not be afraid of landing the T-craft. They do float more, but this is easily managed by slipping. But the one significant disadvantage of the T-craft is that it is too clean, and your only glidepath control is forward slip maneuvering, and this is often not precise enough for spot landings in GUSTY conditions. Throwing the T-craft in and out of a slip takes a couple of seconds, and in rapid-fire gusts, thermals, eddies, low-level micro shears, etc. you can easily get "behind" it. In these rarities, the Cub's excessive drag, and/or flaps if you have them, are a major advantage.
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