I quite like the AC seat on the 787's but apparently there is quite a serious problem with them now and might better be avoided. I had several really nice flights on them, but that's been 3 or 4 years ago.
Deflategate; new executive pods deflating in-flight

To the other part of your question, I too found the LX seats to be a little cramped but I'd still take them over UA on a 788 or 789. LX's service and food were significantly better than the typical I get on UA. I do assume on LX you're looking at a flight on either the A330 or 777? The A340 has the same seat but I remember the video screens being comically small.