Sometimes Wowhead will say that there is more than one option for a set - like there are two pairs of gloves that go with the same transmog set. I think they base their information on artwork/color, but I don't really know how those clever Wowhead people think up all those crazy/brilliant things that they do.
I'm not that clever. Maybe a little crazy.
But I am sort of a bit of a hoarder and I've looked up so many things that I have most of them memorized. I can tell you that while Wowhead says those gloves are both part of the same transmog set, they are NOT THE SAME.
An example is the Bandit Garb set which lists two pairs of gloves that match the set, Ghoul Fingers and Bandit Gloves. Ghoul Fingers are pretty rare to find and go for about 2k on my server. Bandit Gloves, however, go for 250g or less.
But that's not the difference!!
If you want your gloves to flare out a bit at the elbows, you choose Bandit Gloves.
Another example is the Sanguine Regalia (Recolor) set. Wowhead lists two chest pieces - the Thistlefur Jerkin and the Geomancer's Jerkin as parts of this set.
If you look at them side by side, the difference is clear - one has sleeves and the other is sleeveless.
So if you're a true mog-a-holic (hoarder), make sure you check an items actual appearance before you get rid of it!