What is the ruling on loans provided by banks for investment projects, and do they differ from personal loans in terms of impermissibility?

The loans offered by usurious banks are impermissible in Sharia (definition) because they constitute Riba (usury/interest), and they are not considered legitimate Mudarabah (definition) (profit-sharing partnership). This is because, in a legitimate Mudarabah, the principal capital is not guaranteed except in cases of transgression or negligence, and likewise, the profit is not guaranteed. As for loans, the profit is guaranteed in the form of interest taken annually, regardless of whether the project makes a profit or incurs a loss.