After a little thought, I decided to go with Mr. Dave Murray's contribution this time. Its grandness and epicness wins it the prize. Both are great sound-wise and showcase the style of the respective guitarists in a great way, so I had to look to more abstract qualities to decide.
SiaSL is the best. It was the first solo that came to my mind at the beginning of this game, when I tried to guess which one will win. There will be time for analysis of the whole ranking, but I think that these two solos deserve to be in the final.
Two worthy finalists. Both sound like there is thought behind them, while they also are excellent examples of each guitarist's distinctive style. In addition, both are further enhanced by the interaction with the bass line. Finally, both fit very nicely to the atmosphere of the respective songs they are part of.
If I were to select a handful of Maiden solos that I would listen to over and over again, these two would be there, no doubt.
But now that I must choose one to vote for ... Stranger. In addition to being a damn fine piece of guitar work on its own, it is a great example of music that can help create images. During that first part, I can almost imagine standing alone in the ice, staring towards the horizon ... no brave new world.
Ideally, neither. :/ To me, SIASL is highly stylised and relies on that, it doesn't have a lot of feeling. The best part of it is the ending. I'd definitely rather have CSIT any day, which has far more flair and is everything a solo should be. I'm going to have to go for Powerslave, which I find much more enjoyable to listen to, although it's comparatively mellow and isn't as standalone.
Neither of these solos are anywhere near my top 10, but I'll have to go with Stranger here. I really like the solo section, and some of the licks are quite tasteful - though overall I still think it's a bit too stiff. Like Brigiantium said above, it is highly stylised and with that I think it suffered a bit from too much thinking (especially in the more intense section).
Powerslave is a nice solo, but it's main drawback here when comparing to other solos is that unlike Stranger it ends just when the band kicks the song back into full intensity again.
My personal top 10 would be:
1. Rainmaker (Dave Murray)
2. Brave New World (Janick Gers)
3. Gates of Tomorrow (Janick Gers)
4. The Thin Line Between Love and Hate (Dave Murray, 6:54-7:04)
5. Wasting Love (Janick Gers)
6. Sea of Madness (Adrian Smith)
7. Lord of Light (Dave Murray)
8. Fear of the Dark (Janick Gers)
9. Fear of the Dark (Dave Murray)
10. Judas My Guide (Dave Murray, 2:14-2:38)