Has anyone noticed that the A string retains more "zing" than the other strings?
yes. always remember that is a .070, like if it was from a 35-90 set. the texture on E and A strings is a bit rougher compared to D and G, because it helps avoid the "thumpy-dead" lower strings like in Labella's and Pyramid's flatwound (and other vintage flats).
what is the quality that attracts you most to these strings?
low tension and sound.
the price does not makes me feel special, I'm the opposite kind of guy

I can act like a peacock if I can get what I want from cheap gear, but often I smash against the wall of quality.
for example, I'm proud of my Squier Classic Vibe Stratocaster, is awsome, lowest action I could imagine on a guitar (I've had good Ibanez, and this poor Squier kicks them), excellent craftwork, solid truss rod (I adjusted it almost two years ago, with a set of Elixir, and even using it every week at the reharsal and for recording and stuff, it's still firm in it's position), overall good pickups that never made me think about an upgrade. it also enchanted a jazz player i know who immediately decided to buy a couple of CVs.
that's a total win, because prior to this one I've always had good guitars, even tried the American Vintage '62 Strat of a friend of mine, but couldn't be satisfied. this one fills my needs, and 250 euros used... coudn't be happier.
with basses I've never had the same luck

cheap things at least were "good enough", but never that good to cast a shadow above quality gear.
the only thing really cheap I've used with bass was the Harley Benton 40 set of strings. 5 euros, nickel (but opaque like steel, so imagine the quality), I've never ever changed a set because it died. NEVER. only changed them when I got bored of their sound (a bit "anonymous", nothing special), or to sell a bass with new strings.