Notes: Ryanair allows you to choose a first checked bag allowance of 15kg or 20kg. On DUB-NCE it would be €25 for 15kg and €35 for 20kg, one-way, paid online. Starts at €100 if paid at the airport By comparison, Aer Lingus is €15 for 20kg, so make sure you factor it in.

Ryanair requires you pay with the Ryanair Cash Passport and Aer Lingus with a Visa Electron card to avoid the fee of €6 per pax each way.

Ryanair generally puts its fares almost entirely in the "fare" section rather than "taxes", as you can't advertise fares excluding taxes any more, and taxes are supposed to be refundable if you cancel.

Ryanair requires you to check in online and present your boarding pass printed on A4 paper (not letter) to avoid a fee of €60 per pax per flight.

Ryanair releases its schedule whenever it feels like it. I believe its current booking horizon is May 2013. Aer Lingus tends to be more traditional and releases its core routes at T-355 and other routes usually at the start of the preceding season (winter/summer). Each will axe non-performing routes outside of the schedule times if warranted.

Ryanair does not do sales anywhere near as much as it used to. Aer Lingus is running one at the moment.