Is there some reason why you couldn't see both? The AK parade is usually late afternoon (3:45/4pm), and Wishes is always held in the evening (7pm at the earliest)
If you've got any type of hopper pass, you can easily see both without a time crunch at all.
All that being said, if I had to pick one, I'd pick Wishes. I work at AK, and I like our parade a lot, but I like fireworks even more, and Wishes is an excellent fireworks show.