If you have no apparent, immediate need for the AAdvantage
Miles — Starpoints can be converted into a lot of other
airline currencies so it's a more
useful holding currency
than AAdvantage
miles.
Iberia used to have a strange redemption system that used a different
miles value
than most (i.e., you used to earn something like 10 or 20 points on short domestic flights), but since the
airline merged with BA in 2010, things have taken a much more
useful turn.