Yeah the Ab to A sequence has a very particular sound when I play it as well, but it would depend on how you pull it off to whether it will work or not. The Ab to G has more of a familiar sound to it. Since it contains the same interval as the Bb - A.
F-Gb-A has an even darker tone.
Anything goes. What matters is the message you want to send is what you want your music to reflect.
"My whole life is a dark room...ONE BIG DARK ROOM" - a.f.i.