Here my choice is quite clear: Sleeping Sun. This song means so much to me, and was one of the reasons I started looking up more Nightwish songs. The melody is one of the most beautiful I know, and the lyrics are ones I've frequently used in picture collages. Even though I adore Gethsemane, Walking in the Air and Stargazers as well, Sleeping Sun surpasses them on levels of beauty and longing.
I think the original sound is better, but I like the new video more than the old one. Therefore, enjoy the new video with the old sound.