just stats for this season (all games, all competitions, just club games):
Aguero: 41 games, 27 goals (0.66 per game), 7 assists (0.17 per game), average playing time 82 minutes per game
Rossi: 56 games, 32 goals (0.57 per game), 11 assists (0.2 per game), average playing time 80 minutes per game
aguero is about 6 months younger, both are of the same height, aguero can cover more positions (mainly on the wing forward slots), both played for solid teams in la liga (villareal 4th, atletico 5th), both play in thee national team
so where is the 15m price tag difference hiding?