It would also be worth reminding you that the €3000 difference you've stated would be based on quotations for the course minima.
Depending on lots of factors you may find that you 'do not meet the required standard' at 45 hours and therefore the you may end up paying more than quoted.
Other factors - both AFTA and the boys in Limerick will be professional and offer great service so probably little to chose from that point of view. Cork may 'hold you' for commercial traffic which may extend the flight times marginally but will be good experience, something you're unlikely to get at Coonagh.
After you get your licence I tend to find that 3-4 hours covers conversion from something 'smaller/lighter' to a 172. That covers general handling ( stalling/steep turns/slow flight) etc, PFLS, NAV, emergencies and circuit work. Maybe I am a dinosaur but I like to think that you should experience an aircraft in all regimes of flight/possible scenarios before I let you hire one of ours while other establishments seem happy to give you an hour in the circuit and then let you loose!
Travelling time is also a factor - but I'm assuming you're close to half way between the two. If not, there are other airfields around... Birr and Galway (if its still open) for example.
Enjoy your flying
HTH
DD