UA have always looked after me pretty well on many trans-Atlantic trips I’ve done this last three years. In dozens of round trips, I’ve had one missed connection in LAX when I was travelling SFO-LAX-LHR but UA provided hotel, taxis from/to and meals so no complaints there, one cancelled flight SFO-LAX on another occasion when UA pro-actively rebooked me to Burbank and arranged a taxi for me to LAX without me having to ask, and one missed baggage connection in IAD going to DFW but UA went out of their way to get the bag to me soonest. And as far as I’m concerned, UA’s Mileage Plus frequent flyer program works really well too. Given the choice, I would ALWAYS chose UA over LH (and I’ve flown LH more than UA unfortunately).