I couldn't hear any noise from the door vents, they are fairly large so I doubt you'll hear anything from them, unless you have super powerful fans, in which case, you'll hear those instead
As I say, I haven't used the A20, so can't comment there. All the screws fitted to a Lian Li at the factory are usually very tight, so not much chances of vibrating loose.
On the rear grille of the 2110, do you mean the inner or outer grille? I found that the inner grille, the pressed aluminim type can get fairly noisy with moderate speed fans, but is ok with the stock fans. The outer grille is a standard wire grille and that is fine, you really need to leave that one in place in case you need to move the case, it hurts a bit if you don't
Negatives are all in the review