We did all 3 this summer. If I had to pick between PTN and the new WOC, PTN would win hands down. PTN is by far the best Disney parade I have ever seen. It is amazing! Have you seen the previous WOC show? That could make a difference if you have nothing to compare it to. I much prefer the original show; however, if I had never seen it, I might really love this one. To me this one was way too much Neil Patrick Harris- and I love Neil Patrick Harris. My DD(9) however has seen both and she loved the new one. She prefers it to the original because she is currently obsessed with Walt and his life and she loved all the focus specifically on Walt.
I would guess since you are going in the fall that PTN may only run one time in the evening? If it does happen to run twice, depending on the times, you might be able to make it from WOC to PTN and catch both. You would miss the fireworks as they typically start about the time you are leaving the WOC area. We did that our first night. We were planning on seeing PTN on another evening, and I was not looking forward to having to try to stake out a spot as people were staking them out hours ahead of time, so we decided to just pop over after WOC and see if we could find somewhere see it, or at least see it well enough to determine if I felt it was worth the trouble on another night. We went over to DL, did a little shopping, and found a great spot on Main Street just about 15 or 20 minutes before the parade started.
As far as the fireworks, we only saw them from the Fantasmic area- but they were terrific from back there and we loved the projections. We attempted to see them from Main Street another night, but they were cancelled due to wind.