I'd say the SpaceBeds on the A345 and 772 are same same but different. A345 is narrower by an inch or so but has more pitch, about 5 inches more. But the differences are not especially noticeable once you're in the seats. On balance, I do not notice a material difference between comfort on the A345 and 772, so I would let the timing of departure and arrival dictate my choice. The timing of the stop in TPE is fine because you can have a liesurely dinner on the SIN-TPE leg, then sleep right after takeoff from TPE-- or have another dinner before catching your ZZZ's. (The SQ 12 stop in NRT is timed comparatively poorly, breaking up the flights nearly in the middle, which disrupts sleep patterns for me.) FWIW, I'd stop in TPE on the way to SIN (I don't like how early the nonstop arrives in SIN) and take the nonstop back to LAX.