Expert is more suited toward the "during the game" style of play, where you can do anything with any character. However, in terms of gaming for the long run, the regular Sphere Grid has more spaces, and therefore, higher stats.

Ultima and Auto-Life are on the regular Sphere Grid, as Little Blue said. Ultima is behind 3 level 4 Locks in Kimahri's section, while Auto-Life requires a backtrack into Yuna's section.