iShares Core € Govt Bond vs Xtrackers II EUR Overnight Rate Swap

They track different indices: iShares Core € Govt Bond follows Bloomberg Euro Treasury and Xtrackers II EUR Overnight Rate Swap follows €STR (mercado monetario). They also differ in cost (0.07% vs 0.10% TER), replication (physical vs synthetic) and domicile (Irlanda vs Luxemburgo).

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.

iShares Core € Govt Bond has the lower annual fee. Applying the same 7% gross return to both with €300/month, that fee gap alone is worth about €569 after 20 years — that part is arithmetic, not a forecast.

Xtrackers II EUR Overnight Rate Swap is accumulating (dividends are reinvested inside the fund) and iShares Core € Govt Bond 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.