Absolutely IB. Better seat, food, IFE, wines. Never had an arrogant FA in my 10+ or so transatlantics with them, although many have been less than charming.

As far as cancellations goes, this is news to me, and none of the posters provided any data. So I looked it up on FlightStats, which has the last two months data:

JFK-MAD: AA scheduled 61 flights, cancelled 1; IB scheduled 114 flights, cancelled NONE; DL scheduled 58 flights, cancelled 1.
MIA-MAD: AA scheduled 83 flghts, cancelled 1; IB scheduled 57 flights, cancelled NONE
ORD-MAD: IB scheduled 60 flights, cancelled NONE.
LAX-MAD: IB scheduled 21 flights, cancelled NONE.

IB was the only airline which cancelled NO flights. So one more reason for IB in my book.