Much as I enjoyed Sharp's work (and hard work it is, too), it's basically an actor's trick - and one that impresses the groundlings far out of proportion to its worth (like the famous Rain Man performance of Dustin Hoffman). Many people are in enormous awe of visible effort in performance, loving watching actors play an extreme condition.
No one would say it's "easy" to play such an extreme condition, but it's somewhat like donning an elaborate mask and letting the mask do a lot of the work for you.
For me, Boyer's performance is the greater achievement; he's playing a very subtle young man in trouble AND an over-the-top, id-driven puppet monster. And he makes it look like less effort than Sharp's 6-shows a week, sweaty, superficially showier performance (which also relies heavily on truckloads of tech).