I lived and dived in HI for 2.5 years, and somehow or other, my tolerance for the water temps. there decreased the longer I was there! I started off diving the waters in a 3 mm (in winter, no less), but by the end of my time there, I was in a 5 mm in summer and started feeling the chill on my second dive of the day. My husband was an instructor, and he and his mates all dove 7 mm suits with hoods - four dives a day and the wind on the boat, day in and day out, really saps one's body temperature.
If you feel the cold easily and will be diving frequently, take the 8/7. And your hood.