Is it better for the pilgrim to break an investment deposit in an Islamic bank, with the resulting losses, or to borrow from his employer and continue to pay off the debt after performing the rituals?

If your employer offers you an interest-free loan, there is no objection to borrowing from them for Hajj if you are able to repay it. This is based on what is stated in Mawahib al-Jalil: "And if one borrows lawful money for Hajj, and it is a debt upon them, and they have the means to repay it, and the lender agrees, then there is no harm in it." Perhaps borrowing is preferable to breaking a permissible investment deposit if breaking it would result in financial loss, because Islamic law seeks to preserve wealth from loss and waste.