It's been easy for me to get island hopper rewards out of Honolulu rather than LA during the summer months. But in the offseason months for Hawaii, rewards from LA are easier.
I've had one operational upgrade to the Marshall islands, as the island hooper 737 was full.
The diving and exploring on all of the islands (Marshalls to Truk). There are lots of mantas. The fishing can be on/off. Those countries are unbelievably poor and they have been forced to take the money from the Korean and Japanese long line trawlers to empty the surrounding oceans and destroy the coral. And diving the WWII wrecks in the Truk Lagoon is truly a treat.