Depends I guess on the mission to be achieved.I personally think it would be a no brainer for Australia.
8 subs, armed with cruise missiles, that are difficult to find, don't need much support underway, or 3 CVS which are big, need heaps of support, like tankers, easy to find, and easy to follow.
Give us 8 nuke subs please.
if it’s a hit an run, then sure a nasty sub launched missile strike fits the role.
if it’s the much talked about amphib capability mission, then that implies surface assets and their entourage.
be that ASW integrity, counter air or air sea landing capability.
a CVS provides it, gives your task group air mobility, ASW, and if it had onboard long range air to air it could provide ASM defence thereby reducing escort vessel VLS rounds fired and task group resilience in the AO, as well as AEW and perhaps mitigating the air attack on the task group from happening in the first place.