Having a CFII provides 3 additional priv over a regular CFI

1) Ability to provide the 15 hours dual required for an instrument
rating
2) Ability to provide IPCs
3) Ability to provide type rating training not limited to VFR.

Other than that, everything else is just a CFI. I try to take my
private students in IMC at least once. It provides two things 1)
Understanding of what its really like and 2) Better, more realistic,
discussions on outs.

-Robert