401Ks
I have to agree with FormerSanDiegan. It is much better to have the money taken out pre-tax. It drops your taxable income. It removes the income from AGI calculations entirely. This means that if your deductions are being limited for any reason, you still get the tax reduction/effective deduction.
Medical spending account:
This allows you to pay pre-tax and is not subject to the 7% of AGI minimum threshold on schedule A of the 1040.