Esentially AAA bonds are the safest and offer the least return and AA bonds are not quite so safe and should offer a bit of a keener return. The truth is these two classes are very closely matched. If the AAA bond is a treasury bond it will be governed by interest rates so may have a low moment and would be unwise to sell it then (if able to). The AA may be a Corporate Bond not governed completely by interest rates and may just be having a good week! It's a bit of a how long is a piece of string question. Perhaps look at an Industrial long term bond FUND for a decent yield (3-5 years) bye when the DOW is down and SIT ON IT. This will not be a AAA but is a very sound move. A decent yield a decent index (The DOW) and a decent timescale.