epoxy floats are 'gum' rubber. Whatever that means, it's smoother, harder, heavier, and nonporous. The 'regular' floats are softer, lighter, and porous.
IMHO the epoxy floats are not as flexible for conforming to tiles w a non-flat surface. But, they don't stick to grout and squeegie flat tiles really well. If you wipe the edge frequently, in fact, you'll find cleanup is minimal w the efloat.
I highly recommend an e float and an e margin float for edgework.