Which they take of the EIC, and they don't allow the half of SE tax adjustment when calculating income for EIC.
uh...that really depends on your income level.
If you have 2 kids, your eic starts getting phased out at the greater of $22,900 agi or $22,900 earned income. So if your earned income is lower than your agi (ie you have some investment income) a deduction of 1/2 self employment tax that lowers your agi will help give you a higher eic.