Idparocks was comparing "migration" and "immigration", not "emigrate" and "immigrate".  It was Peterpi, not KD48, who first started taking about emigrate vs immigrate.  Before you denigrate someone, who didn't even participate in that discussion, for being ignorant, you might want to actually read the words being compared in the post to which you are replying.

Immigrate - to enter a country of which one is not a native, usually for permanent residence
Migrate - to go from one country, region, or place to another
Migration and immigration (the 2 words idparocks was comparing) are the noun forms. 

Migration refers to movement from one place to another without implying an end objective, immigration refers to inbound migration movement TO a specific place and implies an intent to permanently relocate.  So different words with different meanings, but not entirely unrelated.