I agree with Don. The part I'm not sure about, is the end cost to you since you're in Ireland.
I have the Yongnuo YN568EXs (Qty 3) and the Nikon SB-910 (Qty 2). I've also had the Nikon SB-700. The YN568EX is more comparable to the SB-910 than it is the SB-700, but it's still priced significantly less than the SB-700.
To me, the Nikon flash heads do seem to be much better built, but that 2-3x price difference is buying you more of the Nikon label than it is the better build quality. I use both the Yongnuo and the Nikon units either directly on the camera hot shoe, or matched to Yongnuo YN622 triggers. When using the triggers, I've got the flashes set to TTL mode so that I can control power levels from the camera with the YN622-TX. The side effect of that is that I spend very little time using either flash unit's built in menu/settings setup, so I can't make much of a comparison there. I will say, the instructions that came with the SB-910s were more easily readable than the ones that came with the Yongnuo's.
Starting out, which it sounds like the OP is doing with flash, I would probably start off with the Yongnuo to keep costs down and get more features while learning the technique. In fact, I would probably go the route of the YN560 or YN565 before going with the YN568 even.
If you do decide to go the Yongnuo route, I would also agree with
@Lawrence's suggestion to use Tim Payne's Facebook group for more knowledge on technique and usage. Tim might not be the best for shipping into Ireland, but he does provide a ton of help and is worth checking into.