A lot depends on how tight your rotation is, since MNK can nearly WS non-stop the proc of fire/wind damage is devalued the better you are (higher % of time spent WS'ing).

As far as the GC weapons go the only one I'd think to be better is the LL one with +40 INT at least for Miser's Mistress. The +30 ACC one would most likely always be inferior to Garuda's Claws, and 45 ATK one almost always inferior to Ifrits Claws.

Also it seems that if WS cap is dependent on DPS# Garuda's claws should provide a slightly higher cap around 354-356 STR and 308-312 INT, though at the same time it means if you maintain your stat caps below both weapon's caps they should do identical WS damage which leaves you to only compare their bonus attributes and possible AA damage.

For MM specifically I'd guess LL claws would be the strongest since +40 INT lets you change your gear around enough to gear for either more STR or ATK depending which you need more. Sanction is still stupid though so you'd need to carry around 2 gear sets for incase you die and need to revert to either Garuda or Ifrit claws.

Garuda or Ifrit I don't know which would be better but for MM the Acc is most likely useless and Ifrits +atk should do better than Garuda's +Crit attack. The only thing you'd need to factor is the attack speed / damage difference on AA's and the possibility you can raise your WS's higher if your gear allows you to. Until I either get the claws or see some parse examples I am assuming if your stats are the same for both weapons (under Ifrits #s) then Ifrits should do better, but if you can get past that to 355/312 stat area then Garuda's might be better.

DPS for weapon skill damage stat caps is slightly weird, SE, but it sure allows for different gearing options depending on what type of gear you have available.