My DH has just returned from Dublin with some Cadbury's buttons (not giant, sadly) and dairy milk for me.
Luckily I also have half a bag of British buttons in the cupboard that my children rejected last week (yes, that's right, even children don't like them anymore). So in the interests of science, I can compare them!
Appearance:
The new-recipe buttons are slightly larger and flatter, are a lighter colour and have a slightly rougher look where they've rubbed together in the bag. The old-style Irish ones are shinier and neater looking (if that makes sense).
Smell:
The Irish bag has that unmistakable Dairy Milk smell! The British bag smells of chocolate but it could be any chocolate.
Taste:
The British bag tastes like cheap advent calendar chocolate. And I'm very excited to say that the Irish one definitely tastes how I remember Dairy Milk tasting! It's creamy and more-ish and has that unique Dairy Milk flavour that we've all missed. But I'm not sure if it's exactly the same... there's a slightly odd aftertaste that I don't remember, but it's possible my tastes have changed.
Conclusion:
Irish Cadbury's is infinitely preferable to British!