I disagree.
I mean, what you're saying is that Inter already have a great striking force and adding a quality player like Pandev, for free, is only adding very good depth, while Juve don't need depth but need top class up front.
You are right, but this is a very short term thinking.
Del Piero is 35, Trez 32, Iaquinta 30 and Amauri 29. In a year or so Del Piero might be gone. Adding Pandev for free now to replace Del Piero (not directly, of course), selling one of Iaquinta or Amauri for 10-15m eur, adding some additional 15-25m eur to the money gained from the sale of Iaquinta/Amauri in order to buy a top class attacker.... and you have most of the job done.
But now we'll need lots of money to buy a great attacker and then we'll need more money to buy another attacker (considering the age and the form of all our attackers).