iShares Core MSCI EM IMI vs Vanguard Emerging Markets Stock Index Fund EUR Acc

They track different indices: iShares Core MSCI EM IMI follows MSCI Emerging Markets IMI and Vanguard Emerging Markets Stock Index Fund EUR Acc follows MSCI Emerging Markets. They also differ in cost (0.18% vs 0.23% 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.

iShares Core MSCI EM IMI has the lower annual fee. Applying the same 7% gross return to both with €300/month, that fee gap alone is worth about €933 after 20 years — that part is arithmetic, not a forecast.

Both are accumulating, so on this point there is no difference between them.

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.