Because I do love a definition:

Passive/passivity is defined as:
1. not reacting visibly to something that might be expected to produce manifestations of an emotion or feeling.
2. not participating readily or actively; inactive: a passive member of a committee.
3. not involving visible reaction or active participation: to play a passive role.
4. inert or quiescent.
5. influenced, acted upon, or affected by some external force, cause, or agency; being the object of action rather than causing action ( opposed to active).
To submit:
1.to give over or yield to the power or authority of another (often used reflexively).
2. to subject to some kind of treatment or influence.
To me, it seems to be the difference between "letting" another be in control, and willingly handing over control to another. It is a very subtle difference though, so I too am interested to hear what others have to say. I think whichever pleases you and Keltar, is what pleases you.