There has already been a long post having this same discussion. With this now being reported, there is even more smoke coming from a fire at Aer Lingus! There are several factors that could or are playing a role in this decision.
1. Aer Lingus is partners with American Airlines. Currently AA
has 737-800s on order that it really doesn't want to take on. So, we have a Qantas deal all over again. Aer Lingus will take the 737-800s that AA
can't take on right now. Overall its a bargain for everyone involved. Boeing sells 737-800s to a new customer and therefore becomes it's supplier, American gets rid of contract obligations for aircraft it can't accept, and Aer Lingus gets brand new aircraft.
2. Aer Lingus wants a homogenious fleet. While they are/were working towards that with the A32X, they never completed the movement. Boeing's used aircraft division is able to take in the hoge poge fleet easier than Airbus's. Therefore, EI
gets rid of its current mess and in its place gets shiny new 738s!
This order is supposedly going to be announced this week.
"History does not long entrust the care of freedom to the weak or timid." D. Eisenhower