On his blog, Ben Bernanke weighs the pros and cons of negative (nominal) interest rates vs. a higher inflation target to create monetary “policy space.” His main points are:

• Lower rates work immediately. In contrast, a higher inflation target only works once agents’ expectations adjust. A higher target may not be politically tenable a thus, not be credible. In contrast, “institutional changes … [such] as eliminating or restricting the issuance of large-denomination currency, could expand the scope for negative rates.”
• Both negative rates and higher inflation have negative side effects. But the side effects of negative rates would materialize only during bad recessions.
• There are reasons to expect that higher inflation would impose a relatively larger burden on the “poor” while negative interest rates would impose a relatively larger burden on the “rich.”
• The political risks for the Fed associated with a higher inflation target may be substantial.