Were Christians commanded by God in the scriptures to celebrate Jesus' Death or His Resurrection? Which one?

Good question. Actually, neither. The Bible never gives a command to celebrate Jesus' death or resurrection.  However, the Jesus commands his disciples to celebrate the Passover supper using bread and wine in remembrance of his death.(Luke 22:19) This we do at Easter.   Paul says the Lord's supper commemorates his death until his return (1 Cor 11:26).  This we do "as often as..."    

As for his resurrection, Paul said to Timothy "Remember Jesus Christ raised from the dead...  (2 Tim 2:8).   This is as close as we get to a command.  But the early Christians began to worship on "the Lord's Day" or the day of his resurrection which is effectively our Sunday.  Here we find an application of the freedom of the Christian.  Christians now worship on Sunday and not the the Sabbath.  Likewise. Christians are not required to celebrate Easter or Christmas for that matter.  But Christians began celebrating both, possibly because of the prompting of the Holy Spirit and because of Paul's command to Timothy. 

If we are to "test the spirits" we ask , is the celebration of the birth of Jesus and the resurrection of Jesus anti-biblical.  Well, both stories are contained in the Scriptures.  And there is no command against it.   So Christians are free to remember Jesus in these Biblically described ways.

If the Gospel is Good News, then we have reason to celebrate.  We can celebrate every day!  But the birth of Jesus and the Death and Resurrection of Jesus are so important in this Good News, what better reason do have than to celebrate them!