m308:
Heed NitroX's advice about Woodleighs. The .375 CT is a very under-rated cartridge, it can virtually match the old H&H cartridge's ballistics for the 270-grainer with modern powders, maybe a bit behind with the 300-grainer but not significant on game.

You will be unlikely to need a long shot in most of the Top End, however floodplain country can be very open and the game will be eagle-eyed if they've been chased a bit. I'd go with the Protected Point in that cartridge for the slight improvement in trajectory if a long-shot is needed.

It would be nice to take only one rifle, and even better if you could get the 270-gr Spire Points to the same point of aim as the 300-gr PPs. That long pointy Hornady bullet is a ripper on big pigs, I use it in a .444/.375 wildcat I built on a Lee Enfield action years ago, mainly as a loaner. That rifle has killed a few buff too, with 285-gr Grand Slams I got cheap when Davies Sports closed!