for me it's already 0.2%, so quite a bit of t€ adds up over 10 years
The question is what is better at the same bank
The bank itself or the broker
Depends, for us the Commerzbank was cheaper through the broker (Interhyp) than directly there. Once signed, it doesn't matter. Then your contact is the bank anyway. It might just be that it is not the local branch that takes care of you (they sometimes have their own conditions and the cheapest might be somewhere else), but usually everything is sorted out by phone anyway.
And that's why we preferred to take 0.1% more with the house bank. Contact person always immediately reachable, payout always works within an hour.
Now that everything is clear, the payout also works immediately.
We were somewhat tied to ING because we still had a small residual loan with them that we wouldn't have been able to get out of so easily.