Pose morphs limit your movement to the ones that exist and would cause lag sometimes. On the other hand, joints can be freely moved around using Userdata and XPresso as long as it does not have the Protection tag.
My Toribash rig is mostly made with IK/FK bones and joints, and it is really easy to use and is user friendly[since it has an UI in the Perspective window that can be used to move the mouth's joints, posemorphs or such].
Also, you can drag the tag's name into the XPresso and drag the parameter you would like to use.