I'd agree with everything in there except Eduardo not being as good as Doyle. Eduardo's (0.19 goals to games) stats are worse than Doyle's (0.27 goals to games) in the Premier League so far, but I think there's a couple of mitigating factors there. Eduardo came in from Croatian football and did need a bit of time to adapt. Then of course the leg break. I think if he got a good run in the team and found good form, he'd get lots and lots of goals for Arsenal. His international record is also very good, 18 goals in 28 games. Doyle has 7 in as many games.
Not to put Doyle down at all of course, I really like him, I think he's great for Ireland, but I'm not sure he'll ever be the kind of player that bags lots of goals. The most similar player I can think of is Kevin Davies, a nuisance for defenders to deal with and contributes a lot to the team in terms of build up but not on the end of the move all that often.