I've heard many people over on the Wiki discussing this as well actually. I believe the lightning and winged boots increase speed, however by only such a small percentage. I'm unsure what the scientific boots do, but I can assume the Shelled boots give you some form of a damage boost (take more damage), and the Gladiator Boots probably give a slightly higher damage rating.
This is all in theory, of course. Nobody I've talked to has confirmed if the boots have any real powers.