Prices, connections being equal I would have recommended LX, but hearing that ZRH offers better connections, than I'd definitely go with LX. Travelling as a group of 3 you won't have to neighbor-up with a stranger, whereas (I might be mistaken) on LH one in your party will have to sleep next to another passenger. Not horrible, but a factor to consider. Lastly the BOS-ZHR flight would give you the most amount of time out of any of your stated options to sleep.