Illuminations is my favorite and I have seen it at least 50 times over the last 10 years. I've seen it from just about every possible vantage point around the lagoon and in my opinion, the best spot is on the showcase plaza leading from Future World to the World Showcase Lagoon. This area usually is mostly blocked off for special viewing, parties, or for FP+ but there are always sections you can find open to the general public usually right in front of the port of entry or disney traders buildings. This spot has many advantages including a direct proportional view of the effects and it is the closest spot to the fireworks launch barges making for an incredible and LOUD experience. It also is the easiest exit spot if you are heading to the parking lot, buses or monorail after the show. The plaza area has a slight incline which makes it easy to walk up right before the show - no problem getting a great view.
The runner up spot for me, and the spot I prefer when planning to exit through the international gateway is Italy preferably the osola plaza assuming there is no event blocking it off. For many of the same reasons as the showcase plaza, the vantage point and proximity are superior. There is plenty of open space so lining up before hand is also not necessary (although getting the rail on the osola plaza is worth getting there early if possible).
All the above being said, these places are only marginally better and really, there are dozens of great spots to watch all around the lagoon. I rarely burn time staking out a 'great spot' early in the evening and would rather enjoy walking around the world showcase with a drink (or 2) until just before the show. All the places mentioned in this post are great and I agree, to be aware of the wind direction as that will make viewing (and breathing) much more difficult.