Pro of the Teflon non-greasable: A well made one will be "tighter" and have less slop and play in it, up until the boot decays and dirt and grit gets in there.
Pro of the greasable: A well built one, while looser than the Teflon designs, will be, well, looser.
For the U-joints, I went greasable in my DD, but would go non-greasable (permanently lubed) if I were building a performance machine.
RwP