great question but no easy one asnwer to it, naturally a younger Female will be more firm as her skin elasticity is better as her muscles and tendons are tighter thats a give in, however because the majority of the breast it self is fatty tissue there is a natural loose sway or jostle to larger breasts, UNLESS the chest and lats are worked and tightened up, if there is any doubt in this look up and fitness model and you can see the actual string of the chest muscle in her chest and her breasts standing up and straight outward, along with the muscle tightening the tendons and ligaments helps lift support and firm the breasts as well, you can randonmly look at busty images and see that any 2 women who are a D or a DD one will have a squishy almost flattened look and the other will be rounded and fuller looking obvious some is gene related but working your chest develops the pec muscles which lift as strengthened there in the boobs lift, 3 of the more Natural super firm models you can look up were Virginia Bell, Frankie Hires, and Rosina Revell, these 3 models in particular were D or better and their breasts stood straight out defied gravity , but the little secret no one ever picked up on with them, they had very strong full chests each was able to flex their boobs (lift and lower ) on command, basically menas like Terry Crews they flexed their pecs but on a woman the breasts lift and lower with the chest muscle....I have that ability as well I can flex mine, as far as the women you mentioned comparing, it is a natural thing for women to look over another woman especially in breast area sad to say in a way but society is and has made being busty a more attractive and attention getter and as you guys will attest being blunt you look at our boobs more than our eyes , (why the phrase "hey my eyes are up here" was born, so keepingthe boobs up out and firm is a hidden priority and showing a little extra and strutting proudly of it matters, anyone can say they don't think about it, but ask yourself why as we women intentially purchase the lowest sexiest attention drawing tops and dresses, and why women a littel less than a C cup but push up bras, and why the implant industry is at the highest it has been in decades, firm, full round matters to us as well. same as a great hair do, nails, makeup and attire and bodies, yes soem are less assertive while others will post things like "its ok i know i am hot" cause they can,, another point here to consider, instead of implants a woman can go for a lift, in this a less large CCimplsnt can be surgically placed under the muscle and there in lifts the muscle wall and frame of chest making he boobs stand up and out, and defy gravity likethat of a 19 year old, that said do not think cause a woman is 18-25 automatically means her boobs stand out again some of it is genes and other is toning, but some are as soft and loose and "sloshy" as a 40 year old woman. hope i helped you