The Irish Sea touches both places, so neither is closer than the other.
The sea that separates Ireland and Northern Ireland from Great Britain is called the Irish Sea. The area of sea immediately north of the Irish Sea is called the North Channel, and separates Northern Ireland from Scotland.
The Irish Sea
The Irish Sea, the North Channel and the Atlantic Ocean.
Scotland and Wales, then across the Irish Sea the Republic of Ireland and Northern Ireland.
The Irish Sea or Traditional Name - Celtic Sea
The Irish Sea lies between Britain and Ireland. However, Northern Ireland is part of the United Kingdom, therefore the UK shares a border with the Republic of Ireland and is not separated by the sea.
The proper adjective for Ireland is Irish, for example Irish music, Irish coffee.Irish
The Irish Sea.The Irish Sea lies between Dublin and Britain.
The sea between Britain and Ireland is the Irish Sea.
The North Channel, which is part of the Irish Sea, and the Atlantic Ocean.
The North Channel, which is the northern end of the Irish Sea, connecting it to the Atlantic Ocean.
Ireland is geographically part of the British Isles. So on that basis, there is no answer to the question. What you are referring to is the sea between Ireland and Britain. That is the Irish Sea.