In reply to zimpara:
Depends on your style of climbing.
Scavenger is probably more sustained and technical. Osiris is fairly straightforward to the overhang and then a quick pull through the lip and it's done.
Both have good gear, though there have been accidents (fatal?) on Scavenger due to the gear 'un-zipping' from the bottom - get your belayer to stand close in, or fashion a multi-directional low bit of gear.
Better rope management is required on Osiris and using two is pretty much essential. If memory serves me right, it might actually be easier to use a single on Scavenger?
Osiris has the advantage of the downstairs routes of King Wall. These are tidal, so time it right and do a few routes to warm up on King Wall, before moving to the non-tidal upper tier (Fall Bay Buttress) where Osiris is located.
Additionally, the beach at Fall Bay is better than the one at Three Cliffs.