Originally Posted by corporate-wage-slave

There isn't a benefit on separate tickets on the delay side, even if both sectors were fully BA then they would be regarded as separate contracts. So in a narrow sense once you are in separate ticket land you may as well go for the cheapest ticket. That said, buying a BA codeshare on EI will give TPs, Avios, eligible flights and sometimes a better luggage allowance. So if the difference is small it may be worth paying slightly more. On the down side, EI make it difficult to manage a booking sold outside the Aer Lingus website.