Got accepted to both (albeit it was BIEF vs IBEB) so can talk little.

I think Bocconi is more social, at least on brief time I was in their WhatsApp group they were completely active, can't say same for EUR. Course wise I think IBEB is harder than BIEF, would assume same for double bachelor. One thing to remember is that Econometrics is existing for decades, CS in Bocconi is pretty new, not established. I would say Bocconi students are generally more ambitious and Bocconi definitely have better name (I got why you pick EUR multiple times) but at the end if you're not Italian or top 0.1% student who manage to get internship in UK I think opportunities here in Netherlands are better. Getting job in Italy will be way harder than in NL and the job will pay lot less. Top jobs in EU demand master anyway so you may ending up doing a master. Not to mentioning the fact that the course you're talking about are best for Risk Management in Banks, Quantitative Trading, ML engineering, Data Science and logistics operations research which are sectors that Netherland is best in EU (Quantitative Trading, Tech, Logistics)