Short term fairest paying = PPS pools (Eligius/Arsbitcoin)
These are not PPS! You're misleading people by implying that they are.
They are "PAMSAPWPPSP" (Pay as many shares as possible with PPS payment). As long as they have a positive balance (which both currently have), it is possible for them to pay PPS and they will do so, if the operators don't cheat.
Short term = whatever pool
I disagree, in a proportional pool your shares get worth less and less, the longer the round is. Getting in a 6 million shares round on a proportional pool is eqal to mining with only 25% of your hash rate in a 100% PPS pool (which do only exist if arsbitcoin or Eligius have positive funds - if their funds are negative, you risk not getting paid for some shares or getting paid less than 100% PPS).