First of all, if you had to choose between 8% and Optional Standard Deduction, assuming you had the choice, then 8% is the better rate. :)

Now, if you have to choose between Itemized and Optional Standard Deduction, the decision relies on: will your expenses exceed 40% of your income?

The rule to follow:
If your Expenses > 40% of your income, Itemized is the more tax efficient choice.
If your Expenses <= 40% of your income, OSD is the more tax efficient choice.

Here are some examples to illustrate why:

Scenario 1: Expenses < 40% of Income

Gross Revenue: 1,000,000
Deductible Expenses: 20,000

Taxable Income:
Taxable Income if Itemized = 980,000
Taxable Income if OSD = 600,000

Given the tax table: Tax Due:
If itemized, tax due = 130,000 + 30% * (980,000 - 800,000) = 184,000
If OSD, tax due = 30,000 + 25% * (600,000 - 400,000) = 80,000

In this case, OSD is clearly the better option.

Scenario 2: Expenses > 40% of Income

Gross Revenue: 1,000,000
Deductible Expenses: 650,000

Taxable Income:
Taxable Income if Itemized = 350,000
Taxable Income if OSD = 600,000

Tax Due (using same tax tables as above):
If itemized, tax due = 20% * (350,000 - 250,000) = 20,000
If OSD, tax due = 30,000 + 25% * (600,000 - 400,000) = 80,000

In this case, Itemized is clearly the better option.