Im a domestic customer
ESB I was paying 100euros every two months, now im paying 66euros for the latest BG bill, big difference, I think it depends if you sign direct debit and have Gas with BG already to get the extra 2 % for each, with BG you can get up to 14% off the latest ESB prices (10% for switching and 2% each for setting up direct debit and having Gas with them already), but at least 5% of the current ESB prices for Year two and Three.
AirT im not sure, but im sure if you do a search you'll find loads of info in these treads, best of luck..
If you a domestic customer like myself change to BG at the very least, why should you pay over the odds with the ESB it makes no sence