In the early part of the war, 41-42, Asiatic/Australia is better. Most of the actions is around the Philippines/Indonesia in 41-early 42 and around Guadalcanal/ Solomons in late 42-early 43. You also have generally shorter transit times to your patrol area.
RSRDC will not direct you to a specific battle, although most appear to be modeled. You have to know when they happen so you can be in the area. One thing to remember is that ships will not spawn within 20 miles of your location, so this could affect whether a particular battle occurs.
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