One other distinction: for me the subconscious is about performing (unaware) THOUGHTS and the unconscious is about performing (unaware) ACTIONS.

Examples
UNAWARE ACTION: "Yesterday I UNCONSCIOUSLY locked the door (having to physically turn the key) when I ducked outside to my car for a moment. When I returned to the door thinking that it was open, I was shocked to realise that I had done this".

UNAWARE THOUGHT: "Yesterday I was baby sitting - playing with toys, kicking a ball around etc. When I sat down to write my essay, I realised that I was SUBCONSCIOUSLY thinking about what I should write, and as a result I finished the paper in 15 mins".

Perhaps these are lame examples, but the point is I believe it would be (grammatically) incorrect to substitute the two words in these examples - i.e. unconsciously thinking about my essay OR subconsciously locking the door.

Hope this is clear.