A few considerations might make stock issues more preferable than debt financing. One, is the credit of the operation. If a firm has less than stellar credit, than the terms for lending might not be favorable to the operation.
Stock might be preferable as well if a company thinks that they can buy back the stock in a shorter time period than the terms of a loan.
Finally, stocks might be preferable depending on the amount of money requested. Loans will have fixed terms while larger funds can be raised for stock.