Haha....if you want a good laugh about Mozart being easy/sophisticated, read the thread started by Breadboy. You have to get a few pages into it to get to the hilarious parts.
One thing that Breadboy rather astutely points out, is that Mozart did not ever write anything very virtuosic. But that is simply because it would have gone against the style of his day. For someone with the talent and ability to play the very hardest show pieces, Mozart is quite easy. But for many of us mortals, trying to master the ease, clarity, shaping, and fluidity of Mozart does not come easily. Mozart used to say you should play with a legato that flows like oil. I don't think I've got that one yet.
I do remember it! It is worth looking up. As one of the many mortals (currently working on PC no 9, K271) who has played a lot of Mozart (but never said I mastered it ) I'd like to add a comment or two. "Virtuosic" is relative. I don't think you could really say there is a lack of virtuosity in Mozart's music, although much of it sounds crystalline and simple. The Sonatas K330 and K332, for example-- And the Piano Concertos no 9, and 15-27 all exhibit virtuosity, albeit in a different form than the Romantics.
I disagree that anyone who can play difficult show pieces can play convincing Mozart. They can play the notes, but exactly what you describe as the challenges--capturing his essence--not so easy.Have fun!Teresa