We land at 5:15am in Dublin and plan to drive directly to Doolin. It looks like we could take the M6 or the M7 and I am wondering if there is a reason to take one route over the other? This would also be the case on our return, in reverse. Thanks!
Though most here suggest that you avoid driving right after the long overnight flight, if you're absolutely committed to doing so I'd suggest the M6 ... mainly because it offers a nice enroute stop at Clonmacnoise where you could take a break, coffee-up, and generally recharge at one of Ireland's top attractions.
Another potential stop would be at the Burren, which would also give you a chance to stretch your legs and generally get the blood flowing again.
I've generally found thatr the adrenalin wears off after a couple of hours behind the wheel and the fatigue starts to set in with a vengeance. Do be on your guard for that and plan accordingly to avoid becoming a statistic.