I think Perez is probably a better player than Iwobi but Iwobi has more potential.
Whether he fulfils that potential is another thing, as so many players that have been here have failed to do so, and are now playing for smaller clubs or lower leagues.
Neither are going to win us the PL, and should be squad players, rather than first team starters.
There fact that Perez was bought as cover for Welbeck who was cover for Giroud and Sanchez says more about what Wenger thinks about him than anything else.
When we get a new manager, it will be interesting to see how long it takes him to get a new striker, and how long players like Perez, Giroud and Welbeck stick around.
Personally, I wouldn't start him against Liverpool as we need our strongest team, but if things aren't going our way then he will make an appearance.