Here's a picture of my Avicularia cf. avicularia (cf.=confer). The first pic was when I received her, and the second relatively recently. If I recall correctly, there's a one molt difference between the two pictures.
This is an excellent illustration of a a very relevant point. Some you can, some you can't. In some species, there are no differences visible to the eye, or even to a close up picture. It may be the shape of the female internal sex organs, or the shape of the male sex organs. Things that aren't readily visible in most photos of live animals.
In some species, it may also be that they are morphologically extremely similar to one or more other species, but they are genetically very different.
For a good illustration of these points, I'd invite folks to check out the recent (last year I believe) paper by Chris Hamilton, Brent Hendrixson, and Jason Bond on the Aphonopelma genus.
If anything, Avicularia is at least as convoluted and muddy as Aphonopelma. There's no guarantee that we even know how many species are in the genus. Until someone has done extensive genetic testing on a large number of samples that are taken from all the available populations, we may not know for sure what is and isn't a species in that genus.