Psalm 49, by the Sons of Korah, speaks of the futility of man’s riches and honor in the eternal scope of things. Men build kingdoms and name them after themselves, but eventually they all die and go the way of mankind. When men become rich and their glory increases, it all goes away when they die.
Psalm 50, the first psalm attributed to Asaph, then speaks of the greatness of God. He talks about how God called the earth into existence, and how His voice is like a fire devouring before Him. He will one day call forth and judge the whole earth. He explains the futility of sacrifice, since all the cattle are already His. He instructs the people of God to call on Him when they are in trouble. However, to the wicked God speaks judgement: to the adulterers, thieves, covenant breakers, deceitful, slanderers, etc. If you forget God, He will tear you to pieces. If you praise God and order your conduct right, salvation will come to you.
This juxtaposition of man’s evil ways and God’s perfection and power is just another way to frame the difference between God and man. One psalm speaks of how man will fail and die, even after much earthly success. The other speaks of the greatness of God and the necessity of serving Him. In the grand scheme of things, it is imperative to hitch your wagon to the right horse. The only way to be eternally blessed and secure is to serve the Lord. He alone can lead you to heaven!