Forget the 30-30, and the .243. I have seen far too many Moose walk away after being shot with small caliber, and underpowered guns. While a Moose is not hard to kill, they are hard to kill quick. If the cartridge does not do sufficient damage immediately the Moose can get into water, or go places you can not follow right away. Lost Moose. The .303 is a very adequate cartridge, many moose have been taken by the Canadians over decades of it's use there. I've seen a lot of Moose taken here in Alaska with it as well.
Why even consider the other two when you have a proven Moose gun in the .303.