Not sure which 777 has 8 seats across. The older 777s that OZ uses has a cabin configuration of 2-3-2 in Biz. The QS seats are basically 1-2-1.
Is the map you see have two rows of Biz (row 5 and 6), then the bathrooms, and then rows 7 & 8 biz? If I had to choose, I would go with row 6. I think it might be quieter closer to the front. I know that sometimes OZ puts families with young babies in the first row of Y (row 10) and if the baby starts crying I can't get any sleep, even with the use of earplugs.