Turntable lid up or off?


My Pro-Ject Classic turntable came with a dust cover.  I usually spin vinyl with the cover completely removed and never closed.  Does it matter if the cover is just up or fully removed?  The ultimate test is just listening, but I cannot detect a difference between either mode (up or completely off).
128x128socalml528
Off

I had a Pro-Ject, and always took it off. Easy to do.

My SOTA has no connected dust cover. I purchased a fitted fabric cover for it when not in use.
Off. It will sound more open.
Up will act as an acoustic pickup transmitting vibrations to the table. 
Off. It will sound more open.
Down it will sound closed in. Removed and placed on end it will be balanced. On the short end of course for greater extension. DO NOT lean against the wall, this will be tilted up. The most stable will be horizontal, but then it will be flat. Lifeless.  

What dust cover cleaning solution are you using?