Backstab can only be done with a dagger, so the gloves are more conducive to you if you're using a dual-dagger or dagger and sword/mace/whatever combo. The handwraps do double damage with any 1h weapon whether its a dagger, sword, mace, or axe.
I can't remember if the Double Backstab compounds with the sneak perk which gives you x15 backstab with a dagger. I highly doubt it, though.
So it seems like the gloves are only useful if you aren't spec'd into the x15 dagger backstab perk.
Edited for spelling