Orac, having worked with the AC-130 it's biggest strengths are low CEP for working close to own troops, a LOT of ordnance so it doesn't "Winchester" on a couple of passes and the fact that it's got gas to burn - it won't be at the tanker when you need it most! The latter makes it v cost effective, replacing the need for 6 or so jets and a tanker to be tasked for a deliberate Op.