From your post, it's not exactly clear what your choices are. The thread title says LAX-NRT-LAX, so I assume that's your routing. When you say JAL/AA combo, is that JAL n/s in one direction and AA in the other? When you say AC and NH, is that AC 1-stop in one direction and NH nonstop in the other?

If that is in fact your choice, then my next step would be to look at flight times to see which is more convenient. In terms of the flying experience, NH is better than JAL, but both are nice so it's a slight edge. The choice is really whether to take a 1-stop AC flight or AA nonstop. In business, that's a toss up for me. In F, it would be AA.