One is early in the war, the other at the end. Emancipation Day is a totally different holiday from Juneteenth, having to do with the much earlier Emancipation Proclamation...of 1862. Juneteenth has to do with the freeing of slaves in Texas, 1865.
I’ve heard it referred to as many names over my lifetime:
Juneteenth
Black Independence Day
Emancipation Day
Jubilee Day
etc
I really don’t give a damn what formal name was chosen on the legislation that declared it a national holiday... honestly anyone that has an issue with celebrating the end of slavery in the United States has some serious issues.