So, usually in football lately teams usually play 4-2-3-1 which means 4 offensive players (2 wingers, 1 trequartista and 1 striker).
In our version of the 3-5-2, we use only 2 offensively skilled players in Tevez + whatever striker Conte decides to use.
Switching to 4-3-3 would give us 1 more offensive player, we'd still have 7 players willing to do the work on defence. We're not even asking Conte to use the usual 4-3-3 where you use a trequartista/offensive midfielder as the 3rd midfielder. He can use a defensive work horse in Asamoah there if he wants to, no issues.
But Conte's version of 4-3-3 is not about using creative wingers but really a work horse like Pepe on both sides who is known for his defence and not his offence. That would basically mean taking out a creative player like Vucinic and replacing him with a work horse like Pepe. Basically, Conte's version of 4-3-3 with Pepe offers even less offence than the 3-5-2 we're using today.