Firstly, this is Prince's best work from the perspective of coming to the album alone. Prince effectively did everything - instrumentation, singing, and songwriting. Only mild outside influence comes in throughout Sign "O" the Times, allowing Prince as a soloist to stretch his legs and see how long they really were. The height of his invention is all over this album, with him single-highhandedly reaching into his mind and pulling out every possible sound he could throw in and somehow making it all flow throughout. Not only does he perform alone, but he also does so successfully.
Secondly, the creativity of this album is expressed through Prince's constant ability to refuse to be boxed in. Sign "O" the Times is not any specific album, much like his major success Purple Rain, but to an even greater degree. The latter took multiple realms of music and blended it in with pop. Here, Prince isn't as much a pop icon but a universal mastermind; it feels like virtually everything falls under the scope of this record, nothing out of bounds. Much like his ability to perform it all alone, that he could virtually perform any given style of music makes this effort even more astounding. Playing all the instruments for a three-piece style rock album is impressive; playing a death-defying deluxe album alone is a whole different ball game.
Keeping up with everything occurring throughout is impossible on Sign "O" the Times. There is so much transfer from sound to sound, emotion, and style that to many you might become exhausted by the end of the album. Purple Rain therefore, to many, is likely the easier to consume album, thereby an easy favorite. That the albums are so different yet coming out of the same mind should be enough to exhibit the talent behind the music, but comparing the two albums is probably not recommended. There are so few similarities between the two that they exist on completely different planets; one a planet where Prince is the star, and one planet where Prince is the virtuoso.
Regardless of which album defined the era more is effectively moot when the conversation turns to Prince being the artist who defined the era broadly speaking. Much like Stevie Wonder was for the 70s, Prince was an artist who could hold himself at the top of the charts while maintaining his technicality and impressive acumen. An artist who deserves every single amount of praise he receives and then some, Sign "O" the Times is the kind of album you really could never stop hailing for its versatility and quality.
Favorite track: Hot Thing