why not try both personally im using slate caves from now on when i get me funds back up if you are going to use pvc pipe make sure you cap one end of it.
are these in a breeding tank or comunity tank etc
mine bred in between the glass and a plantpot not much room and lost alot of eggs as he was trying to cover them when anything was coming near and in the meantime flicking eggs out
IME breeding them, they will breed anywhere they feel safe and somewhere that, usually, is inaccesible to other fish. one of my boys bred in an ornament that had a hollow part inside. just depends i think