You have a pile of legacy code that’s hard to modify, hard to test, and never seems to be bug-free. You have some testers who are available to be moved to the front of the flow to write regression tests. Is it more cost-effective to have them write regression tests for current features or for new features? Does the answer depend on aspects of the environment, or the tools available?
I must admit I’ve always tended to favour testing the new stuff; what would you do?