Actually, yes - from an engineering standpoint it's better in pretty much every sense. Stiffer, less resonant, reduces distortion. Whether or not they're audible is a different question... Sometimes it is, sometimes it isn't.
Hmmm. Aluminum is an elastic material just like steel. It has about one-third the density of steel, one-third the strength, and one-third the modulus of elasticity. But it is still elastic up to its yield point. And with aluminum, you don't want to ever get anywhere near its yield point or it will fatigue badly and crack.
Cast material is often more brittle than cold-worked material.
So, an aluminum basket that is lighter than a steel basket will be less stiff, though the shape of the casting might put more material (and stiffness) where it does greater good and less where it isn't needed. I have this feeling that this is rarely designed based on material principles but rather on aesthetic (and cost) principles and then tested with adjustments as necessary to fulfill functional requirements.
Plastic can be light and strong but it also tends to creep, even when reinforced with, say, glass fibers. Carbon composites can be designed to minimized creep. A lightweight basket suspending a heavy magnet out in free space seems like an invitation for long-term creep to me.
Material science is far less about the material properties than about the shape and design of the structure and how it accommodates those properties. This is why speakers should be evaluated on their performance rather than their structures.
(I'm not commenting on whether the iron in steel affects the voice coil EM field favorably or not compared to alternatives--not data in my possession--but I'll bet even that can be compensated for.)
But aesthetics matter to some folks, and
de gustibus non est disputandum. I suspect that's especially true at higher price points, though the cabinetry and exterior finish would normally be the primary part of that consideration. I've managed to avoid higher price points fairly well in my choices, and been happy to live with speakers that look okay but are not works of aesthetic art.
Watches are a whole other thing (he says, wearing his Breguet XX today, which can have no functional justification at all but who cares?). And my tuba is beautifully made (and Swiss) and was priced such that I expected beautiful construction as well as superior musical capability. So, what do I know?
Rick "whose speakers had to pass the WAF but doesn't even know how the baskets are constructed" Denney
Thanks so much for the contribution 
