Minor correction- the good info came from MT, alan. Just to give credit where it's due, like.
On the other subject- this is a discussion forum, and a place where people sometimes get answers to questions if they don't know themselves. But to state baldly that it's for an essay tends to send entirely the wrong message, particularly when many/most people are fairly busy with their lives elsewhere. It just comes across as laziness.
It's a pity, too, as had this been phrased differently it could have turned into an interesting discussion. Not that I'd have been able to contribute much, but I'd have watched it keenly. I learned a good bit from MT's post, for example.
Is the info you require really that hard to find? Surely the RSUA have publications on Northern architecture dealing with themes, evolutions, etc, and I know there are many books tracing the progress of architecture in the RoI in the 20th century. And the UAHS publishes many books, pamphlets, etc. on the more historic aspects of the North, some of which might deal with the 20th century. Compare the pictures, assess the architects. Use your eyes. If there's a difference, is it down to partition? Or is it simply the extension of the regional variations found throughout the island? And if there's no difference, is that because architecture generally is becoming more international?
I don't think it's the fact that you asked this question, it's the way it was asked and the presumptuousness that we'd simply give you the answer you require - as if we were waiting in the wings to lighten your workload - that bothered us (well, me anyway).
Most importantly, you'll learn more by doing it yourself than by having it handed to you on a plate.