Just to be clear, LiFe are NOT the same as A123s. A123s are LiNP. A123s are a better choice for high dollar airplanes. LiFe batteries come from a number of different sources and may not have consistant quality.

The choice should be between A123s and LiPo. I wouldn't consider LiFe, unless the source is reputable. Even so, there is no disadvantage I can think of with A123s.