In most games I’ve seen Jap take Sol early, but at some point the Anz/US will take it back and build up there. Its even worth putting an AB there to help protect your fleet. It will give the allies some mobility. If Jap strikes at Aus from Car you can either attempt an invasion of a weakened Car, or counter attack the Japs on the Aussie coast. If the Japs attack you at the Sol, you might be able to deliver a knock out punch from Hawaii, with a clean up crew from Aus.
Its all about having options with the allies, and counter attacks. You might sacrifice one lamb to draw in the wolf, then the hunter becomes the hunted.