Which sonata is technically not too hard?
And what do you think of the second sonata in particular?
Compare any of his sonatas to one of his operas or concerti and you begin to see the obvious weaknesses. His efforts in this direction were rather uninspired.
Opt for Haydn if you need to master a classical sonata. Infinitely superior to Mozart's rather pale efforts, with maybe the exception of the A minor sonata.