Easter commemorates the death and rebirth of Jesus Christ. The crucifixion of of Jesus was an act of sacrifice believed to wash away the sins of the world (hence the term "Lamb of God", as before this, sheep were sacrificed to wash away sins). Christmas simply celebrates his birth.
Now to many Christians, Easter is more important, as the act it commemorates was the most important act of Jesus, according to Christians. However, many Christian denominations, such as the LDS church, shy away from making the death of Jesus more important than his life. This stems from not wanting to believe that it is not their actions that allow them closer to God, but simply by the grace of God (hence their believe in the "levels" of heaven).
I am by no means a theologian, but have been a non-denominational Christian most of my life, and have friends of many faiths and denominations (mostly Mormons).