I'm surprised that more knowledgeable folk ain't replied to this yet. Here's the things that I can think of off the top of my head:
1. PH
2. Sizing
3. Texture
4. Chemistry unrelated to PH
You can change the PH of paper to make it nuetral or acidic and you can size paper to change the way it absorbs solution but some papers just won't work no matter what you do. I've done everything I can think of to make Arches Hot Pressed watercolor paper make a decent print but it won't (I've got a huge stash of it for non photo use is the only reason for beating my head against that wall).
Texture is what it is, some images I think work with the loss of detail that a more textured paper gives. But I think in general most people keep to the smooth ones.
I'm going on my own voodoo experience but I think some papers have something in the sizing or the rag itself that just don't agree with sensitizing solution.