That all depends on what you are looking for. The west and north west is more traditional Ireland with a a lot more Gaelic being spoken. If you are looking for good broadband then being out in the sticks may not be such a good idea. The mobile signal coverage is reasonable but there are black spots and the north west is one of them, with the exception of Galway City. You are obviously used to open country side and the Donegal will certainly give you that.Looking Donegal, Sligo etc. but open to suggestions.
The better weather is had in the South East and personally I think the best scenery is in the South West. Come and have a good nose round before you make your mind up is probably the best way. If you make it down to Wexford, give me a shout.