Nick
"Is it the songs themselves or the style that they are performed in"?
Neither; it's the process that the song has undergone once it is passed on from whoever made/wrote it.
The songs have been passed on through time and distance - so much so that is virtually impossible to tell where they originated.
They have been adapted by those who took them up, quite often to fit the new circumstances.
A song say with a sailor as a main character turns up altered to say, a soldier, or a farm worker, or a miner.
At the height of the tradition styles probably differed from place to place, but as it died off singers tended to be remembering them rather than performing them and many of the stylistic elements disappeared.
It is debated whether the English tradition was ever ornamented, yet in Ireland, where much of the repertoire was brought in from Britain, many of the singers use a great deal of ornamentation.
English and Scots songs tend to be straightforward narratives (stories), while in Ireland the songs are more lyrical, ie. contain much more description and commentary which is probably superfluous to the main stories of the songs.
""Does that matter?" depends on your interest - it is to me, it may not be to you.
Jim Carroll