Make sure to factor your own time and peace of mind into the calculations.Brendan has for years advised to buy I think 10 big hitters and hold forever. At this stage I agree with holding a portfolio of shares but a much larger amount.
If you’re trying to replicate a world index or even just a US index, you will need to spend time each year determining if your basket of shares needs to be rebalanced and dealing with dividends and cross border taxation etc.
Unless you can really disconnect from it, you will most likely end up paying a bit of attention to the performance of the companies in your basket. You might enjoy this, but many people find it stressful, particularly in bad years, of which there will be many. You might get lucky with your basket of 10 to 20 shares, but you also might not and suffer the stress of watching a stock/vertical/region you’ve invested in drop significantly and stay there.
Balancing all this and the uncertainty of the future taxation of esoteric stuff like US ETFs and Investment Trusts, I personally decided the set-and-forget nature of a single ETF was well worth the potential extra cost. Will I end up with the biggest possible pile of money at the end of my life? Maybe not. Does that matter? Definitely not (to me).