Can’t resist repeating myself until it’s been hammered into everyone’s head… 
The 15% lost figure is true for U.S. dividends (from U.S. corporations) “only”.
Whereas U.S. should only make up about half of VT/VWRL/VWRA.
So it’s probably more like a 7-8% figure on basis of the whole fund - notwithstanding that the Irish fund could be more tax-efficient on other countries’ dividends.
Of course, with a 55+ percent share U.S. securities in an All-world ETF, the taxation of U.S. dividends should effectively decisive factor in determining the most tax-efficient fund domicile.