Can we please stop comparing players who do not play even remotely the same positions.
Jovetic is a huge upgrade over Vucinic. The kid is very good with his back towards the opposition goal, has good technique, good vision and in addition to that he's much more composed in front of goal than Vucinic when facing a goal scoring opportunity. He knows the Serie A and will be surrounded by much more talent here than he has ever been at Viola. Furthermore, he's far from reaching his peak as it is, and he's already better than Mirko. He does what he does on a consistent basis and has a pretty good work load.
Higuain would be brought in as a replacement for Llorente, which seems like a silly way of prioritizing when we need an secondary striker to do what Mirko does on his good days on a consistent basis, with added stamina.
We're talking two distinct categories of strikers here, Vucinic and Jovetic are in their own box while Llorente and Higuain are in their own box. A lot of our attacking play is built upon the foundation of having a Mirko-type in our team, which means that if we played Higuain - Llorente up top, that would bring a whole set of new issues to adress.