Well Pembrokeshire is on the west coast, and Norfolk is on the East coast.
So if you are coming from N Ireland I would have thought somewhere on the west coast would be easier for you to get to.
Both areas have their beauty.
Pembrokeshire has the national park, which was I believe the first national park in the UK, and has an amazing rugged and dramatic coastline
Norfolk is also lovely, with plenty of quiet areas, huge beaches, and lots of wildlife and birdwatching.
If you love nature and the outdoors you will like both areas.
If you are looking for wild nights out then neither of them are for you !