Myth myth myth, I have a good amount of experience with this and have even had several grows myself, they are both the same!! Anyone who tells you the caps are stronger please tell them to just sell you all of thier stems for cheap LOL. What the guy above me said is true though, the stems are often very hard to choke down especially when bone dry, they want to cling to your throat all the way down. While the caps kinda Crack into crumbs when you chew on them.
personally mushrooms don't seem to have the same amazing visuals as the other substances I've tried, it's just way you more of a mind fuck and I mean TOTAL mindfuck. The visuals to me just seem very sinister where everything is curved, edgy and pointy. It defiantly has a jokerish quality to it. But as to the original question the entire mushroom is all the same done worry if you are sold just stems or just caps. Just worry about the potency of the the shrooms that were grown.
Happy shroomin!