Other random tidbits:
- They don’t track the same indexes: VT is FTSE Global All Cap, VWRL is FTSE All World.
- They don’t have the same holdings: VT has 9318 holdings, VWRL has 3782. AAPL, the biggest stock in both, makes up 3.68% of VT and 4.10% of VWRL.
- They don’t have the same dividend yield: VT has 2.33%, VWRL has 1.99%.
- They probably don’t practice the same securities lending policy.
You may have taken that into account in your calculations, I haven’t checked. I’m just pointing it out to underscore that the tax treatment of dividends is but one piece of the puzzle.
Also to note is that US stocks usually have a lower dividend yield, so dividends are not evenly distributed accross countries by market cap (there again, you may have corrected for it already).