I don't really agree that Giovinco was more talented than Marchisio, even if his style of play makes his talent a lot more recognisable. But even if he was more talented, talent alone means very little, if anything.
Other than that, there is some truth in your statement. Both players went to Empoli, subsequently returned and, as we all know, one of both players managed to convince every manager (let's not get into which of these managers were terrible, which ones were idiotic, etc. We're all well aware of the results) we had since then, while the other one never did. So yeah, Marchisio has had more oppurtunities to develop.
Which brings us to my main point: According to (almost?) 50% of the people on here, the fine & promising young player we spent most time on so far, actually isn't worth being on the team in the first place.
Hindsight is a beautiful thing. Can you imagine if we had sold or loaned Marchisio 3 or 4 years ago? I'm pretty sure no one would have agreed with that.
This being said, I do not think we need to get rid of Sorensen. I don't agree with people saying he had a good season, but considering the state of the entire team, I definitely saw enough potential in the kid.
Edit: reply to Nenna, obviously