[olddog]

If your not going IRS, and you are going for much over 400 hp or if you plan to hammer it hard with sticky tires, the 9" is the way to go.

Knowing that no matter how mild you build it, you will likely want more later. I would go for the 9" everytime, but that is just me. I wouldn't toss rocks at an 8.8" as it is a decent unit.