I am not an expert in this area. Following are just my observations concerning the these two groups and the differences in their cultures.
Although there are many overlaps in their history and culture, they are two distinct groups. They differ in language, culture and to a large degree in religion. The Scots tend to be more inclined to Presbyterianism, whilst most Irish are Catholic in orientation. Yes, there are some exceptions with Scots Catholics, and some Irish protestants. The wars over religion in those areas were highly contested. In my opinion, the Scots tend to be more independent thinkers, whilst the Irish culture tends to be more community oriented.
Although both groups are closely connected with the land they come from, there are some distinctions in their histories and culture that require some lengthy study in order to appreciate. In an over-simplification, the Scots tend to have roots in Pictish/Caldeon tribes, whilst the Irish have their roots in other tribes. The tribes often alternated between warring with each other to joining one another against a common enemy (which was often the Vikings).
The type of tribal structure that developed in each nation was also distinctive. In Scotland, the clan system developed, which was different than the tribal system that developed in Ireland.The ruggedness of Scotland and many isolated areas led to different structures developing in these areas. Although both groups developed legal systems, the Brehon system used in Ireland seemed to be developed, standardized and widespread than the legal system developed in Scotland which was largely driven by the strongest clan leaders.
The invasions or attempted invasions by various groups also shaped each nation differently. The Scots maintained a fierce tendency toward independence and managed to fight off many of the invaders.
The Irish also love independence, yet were not always as effective as the Scots in organizing their efforts.
The different cultures have led to different views of what constitutes whisky. Each makes their own type. They also have different cultures. The Irish have developed their music, poetry and story telling to a greater degree than the Scots. The Scots have managed to accomplish some amazing scientific advancements and literary achievements more so than the Irish.
These are just a few of my observations. I hope that it helps.