There were three Gaelic Ulsters: there was eastern-Ulster (Antrim and Down) which had been intensively developed in the 1200s as an Anglo-Norman colony, and that colony had collapsed later and the area seemed never to have recovered. Certainly by the Elizabethan period it was the most under-populated part of Ireland, and though much was very good land, land eminently suitable for settlement (and this is, I think, why it attracted such a high proportion of settlers in the 17th century) simply that the native population in Antrim and north-Down, was relatively thin on the ground. And this is perhaps why they put up so little resistance to the settlement because the lordships - the native Gaelic lordships of the area - were not very well established in a solid economic base.

And then you have the Ulster borderland (Monaghan and Fermanagh) - Cavan incidentally was not regarded as part of Ulster until the Plantation: it was regarded as part of Connaught - but Monaghan and Fermanagh were much like other parts of Gaelic Ireland, they had much more in common with other... they are relatively well-developed, they have links with the Pale, and with gaelicised English lordships of the midlands and with Cavan; and so they fit more into the general Irish pattern.

And then Tyrone and Tyrconnell and Donegal are something in-between. They are perhaps relatively under-developed or relatively pastoral economies (though not entirely pastoral, not entirely given up to grazing) but I think the reason why they are relatively under-developed is there were no merchant communities near them: the nearest merchant towns were at Galway in the west and at Carrickfergus in the east. And therefore, they didn’t perhaps participate in the economic upsurge of Ireland which took place in the late 1400s and from then on, until the wars of the late 16th century when foreign trade developed.