At the molecular level, gelatin is exactly the same as hide glue put in a purer grade.
It's not often made from hides, mostly from bone scraps.
Gelatin is what you get when collagen is broken down into smaller parts (the stuff composing all connective tissues in hide, fascicles of muscles, sinew, gut linings, bones, blood vessels, ...). So you could make "hide glue" from any of those base ingredients.
Sources may vary, but the final product is extremely similar. The purer grade, the better it should stick.
I prefer gelatin leaves over hide glue granules, because the thin leaves dissolve faster than the granules.