For Wishes, it has to be right in front of the castle to watch and get the full effect. We have also watched from the top of the train station, but for the photo montage, that is a bit far away. I agree that the crowd at the end is awful, but we just move along with it, and once you get out of the park it's no problem.
For Illuminations, we used to always like the bridge at Mexico the best or that little park near the Rose and Crown. The park near the Rose and Crown has not been available for a few years now, and you have to get a spot on the Mexico bridge very early. Now we tend to gravitate toward the end of the walkway from FW to WS, and get a nice spot there between the two sales areas.