Morata is 22, and starting to fulfil his potential, playing very well, and working his way into the starting line-up of the best team in Italy, and a CL contender.
Immobile is 25, should be in his prime, playing terribly, and has been benched by the 10th place team in Bundesliga, he hasn't started a match in 6 rounds.
People overrate Immobile based upon 1 good season. Just 1. Klopp and Dortmund fucked up in that regard too. So did Prandelli in taking him to the WC.
People said we overpaid for Gio at the time of his purchase. 11 mil for half. Immobile sold for basically 10 mil for half very similar.
In looking at the year prior to our purchase of Gio, and also the year prior to our sale of Immobile:
Giovinco in 2011-12 (age 24->25) 36 games ~ 15 goals - 16 assists
Immobile in 2013-2014 (age 23 -> 24) 33 games ~ 22 goals - 3 assists
Is Immobile's season really any more impressive than Gio's? Gio had 15 goals - 16 assists. I'd take that over Immobile's 22 goals - 3 assists any day. The problem here is that like with Immobile, Gio only ever had 1 single good season, and it was at a mid table club.
These two players are both examples of having a good season well into their 20s and being massively overrated because of it. We got bitten by our stupid purchase of Gio, and didn't want to have it happen again with Ciro.
Hence the reason we went for a much younger player, with massive potential in Morata.