I see them as complimentary not in competition with each other.
JSM/NSM as a harpoon replacement. It also fits inside the JSF internal bay. It has a small warhead and limited range. But it is entirely likely the 8 harpoon launchers could be replaced with 12 NSM launchers. On basically any platform (Anzacs, AWD, future frigates, possibly even OPV's). It is likely to also fit on platforms like P8, F-18's (four on a super hornet) etc. NSM can also be sub launched.
LRASM is more like a tomahawk replacement it is nearly three times the weight. It doesn't fit in the F-35, if it was used as a harpoon replacement it would be limited to larger platforms and would occupy VLS. I don't see fitting 12 LRASM to the AWD or the future frigates as part of a regular load out, it would compromise the rest of their missions. While Tomahawk has a longer range, IMO for Australia that additional range isn't really important, if we had LRASM I don't think there would be any reason to acquire the older and less capable Tomahawk.
But 12 NSM + say 4 LRASM gives a very significant anti shipping capability (as well as the anti shipping mode of SM-2/Sm-6). Or land attack. If circumstance require more, that can be accommodated.
It's always an interest topic of what will replace Harpoon as the future RAAF/RAN AShM, and there certainly appears to be a number of options, or even a 'combination' of options for the two services.
Firstly, whenever I see NSM/JSM mentioned together, I think it should be pointed out that they are not the same weapon with a different name.
NSM (download the PDF brochure)
https://www.kongsberg.com/en/kds/products/missilesystems/navalstrikemissile/
JSM (download the PDF brochure)
https://www.kongsberg.com/en/kds/products/missilesystems/jointstrikemissile/
Yes JSM is an evolution of NSM, but it's not the same missile, you can't put an NSM inside the weapons bay of the F-35 like JSM (which can also be carried externally too), that's not to say that the ADF can't have both, but still they are not the same weapon.
Similarly for LRASM, it's an evolution of JASSM-ER, which is an evolution of JASSM. We currently have JASSM in service on the Classic Hornets, and potentially we could have JASSM-ER and/or LRASM in the future service too.
Currently of course Harpoon is the AShM of choice, Classic Hornets, Super Hornets, Growler(?), AP-3C and I also understand the RAAF's P-8A is also going to be Harpoon capable too. For the RAN it is FFG, FFH, AWD and the Collins fleet.
For the future, well I think we might actually see a broader combination of AShM's, not just the one type (eg, Harpoon), across the two services.
JSM
I can certainly see JSM as being the weapon of choice for the F-35A fleet, carried both internally and externally, there has also been fitment trials on F/A-18F, but not integration as this stage.
And who knows into the future, possibly a future replacement for Harpoon on the P-8A fleet.
NSM
I can also see box launched NSM being a future replacement for the 2 x 4 canister launched Harpoon on the AWD's and also as the 'original' fitment for the Future Frigates when they start to enter service in the late 2020's or early 2030's, and also box launched (which keeps the Mk 41 VLS free for SM-2, SM-6, ESSM).
LRASM
When it enters US service it will initially be capable of being launched from B-1B and F/A-18E/F, which means integration onto the RAAF's Super Hornet fleet would be seamless too (and potentially external carried on F-35), and of course surface launched via Mk 41 VLS, and I also understand testing has been done from box launchers too, which also potentially means it can replace the tube launched Harpoons without taking up VLS cells.
SM-6
Whilst obviously primarily for long range air defence, it will have an AShM capability too.
Future Submarines
This is going to be an interesting one as to what will be the replacement for sub launched Harpoon. We could potentially see versions of both JSM and LRASM being available in the future too.
The RAN and RAAF are certainly not going to be short of options, or combination of options for air launched, sea launched and sub surface launched AShM's.
Will be interesting to watch in the coming years!!