A 10 footer can be an advantage in a floattube...not that i am higely experienced with tubes (well..work with a few

) but I found a 10 footer helped keep the line off the water during the back cast.
By theory, a 10 footer should generate more linespeed and hence cast further....if all things are equal that is
A 10 footer would also allow better control of a fly line on a river by allowing better mending and the ability to hold line off the water.
However, a 10 footer is a disadvantage when using very heavy outfits such as 10 weights as you have more leverage on your arm.
Me..I have both 9 and 10 footers...from 3 weight to 10 weight....the difference between a 9 foot and a 10 foot 4 weight is not noticable to me, but the difference in a 9 foot 10 weight and a 10.3 10 weight is huge!
Lastly..my 10.3 outcasts my 9 foot 10 weight buy a fair bit when using shooting heads...so..in conclusion...who really knows..lol