Hi Debby, I'm late to the party (as usual). I'd been busy with work the past many weeks, and had not been checking this board. After "friending" you I figured I'd better pop in; I've only skimmed the numerous posts in this thread so I'll read it more carefully in a little bit and see if there is anything I can contribute regarding living/diving on the Hilo side.
In general, the diving on the Kona side is more "reliable". This is because Hilo is on the windward side. Fewer dive days in Hilo, and generally less "viz" than on the Kona side... but GREAT diving on this side when the weather is favorable.
Leleiwi is the best spot in Hilo, about 10 minutes from downtown. It has an extensive reef structure, a huge and healthy turtle population, and a fairly easy entry and exit off of a low lava shelf (like sitting on the edge of a pool and "skooching" in). But surge, reduced "viz" and sometimes a deceptively strong surface current (especially in the winter) can make diving at Leleiwi (and many East Hawaii spots) tricky.... many folks have dove at Leleiwi and had a ho-hum experience because they dove on a murky day, and did not really get to see what is there.
We'll often drive to Kona or Kohala to dive when weather in Hilo is so-so. The Kona side (and Kohala) have some remarkable shore diving sites.
Feel free to post questions in this thread, or send me PM's and I'll try to answer any questions.
Best wishes.