Personally I find I get more out of the former technique, as I am more experienced with it, but there is a problem in that it is very straining. It takes a lot out of the magician. The shewstone, however, acts as a kind of conduit. It alleviates some of the strain on the seer by employing a half-way house for the images, thoughts, and so forth to emerge.
When it comes to Enochian the more conduits available the better, particularly when the shewstone is placed on top of the Sigillum Dei Aemeth. The Sigillum, when opened (the easiest way to do this is an invocation employing the names within it), provides a vortex which feeds into the shewstone, not only empowering it, but allowing a clearer and more accurate portrayal. One of my "rules of thumb" is that the Sigillum be employed with the appropriate invocation and prayer for truth, as many magicians have been led down the dark alleys of illusion and fantasy.