Wondering, should both items be documented? Or, is it 'obvious' that if a person immigrates to somewhere, they had to emigrate from somewhere? (Considering no time gap) Does it become obvious that if born, say in Poland and immigration noted as arriving in New York?
You should document both when you have the information.
It's possible that a person emigrates from one country, spends some time travelling, and then immigrates to take up permanent residence somewhere else. It's also possible to spend some time in one or more interim countries as a "temporary resident" without actually immigrating there and then emigrating to the final destination.
Usually, when you have information about an emigration, you know the port of embarkation and the ship's name. This is often different from the place of residence, and is always useful information. Port of immigration is also useful to know.
I am fortunate to have found the ships used by a group of my wife's ancestors going to and from Australia. They spent a few weeks on the boats, and additionally had a number of stops on route. While some of the information is probably irrelevant, since it IS available, recording it makes sense since it may link to other events later.