i would say hammer since even without element its pretty strong, and charge-land-pound tactic is pretty useful on rathalos oh, and hammers are pretty fast too
charge-land-pound: tactic available for hammer and gs
1st step: wyvern about to land/fly,for rathalos
2nd:you stand on his shadow
3rd:charge your weapon,timing is needed for GS
4th:wyvern land
5th:pound his head/slash his tail
side note:
-charge gives you anti-wind,pretty useful
-if he does not flinch after you pound his head do not try it until you get a better hammer
and as you already know,strong single blow is best against rathalos/ian