LOT is okay if you're going to WAW on a 787.... but its a bit out of the way if you're heading to Western Europe, and it has fewer connections than the other airlines.
It's also always dangerous to book a flight when only a certain kind of aircraft that the airline operates is good. (I'd say this goes for a lot of LH routes too.) If you get on a 767 instead of a 787, it's basically the old LH business recliner. With OS or LX, you are pretty much guaranteed the new seat.