Vanguard FTSE Developed World vs Xtrackers FTSE All-World

They track different indices: Vanguard FTSE Developed World follows FTSE Developed and Xtrackers FTSE All-World follows FTSE All-World. They also differ in cost (0.12% vs 0.15% TER), replication (physical vs physical) and domicile (Irlanda vs Irlanda).

Nobody can know that: they track different indices, so their returns will diverge, and past index performance is not a prediction. What you can control today is the cost, the tax structure and whether the index actually covers what you want exposure to.

Vanguard FTSE Developed World has the lower annual fee. Applying the same 7% gross return to both with €300/month, that fee gap alone is worth about €565 after 20 years — that part is arithmetic, not a forecast.

Xtrackers FTSE All-World is accumulating (dividends are reinvested inside the fund) and Vanguard FTSE Developed World is distributing (dividends are paid out to you). For long-term compounding in Spain, accumulating usually defers taxation; distributing gives you income you are taxed on each year.

Yes. Unlike two funds tracking the identical index, these give you genuinely different exposure, so holding both is not automatically redundant — just be aware you may end up overlapping on the largest companies and doubling your rebalancing work.