I feel obligated to mention the wiki's
material science page. Idk whether it's still up to date, but I assume a good chunk of this still applies.
Tl;dr: weapon quality
does matter (it gives a multiplier on accuracy), but weapon density has heavily diminishing returns. If I had to guess why:
Since momentum = velocity * mass, and lighter items can be swung faster, attack momentum is largely independent from weapon weight.
The momenta tables on this page also indicate this. I believe it is because the density itself is a small proportion added to a separate value:
M = 0.06 * Str * Vel / (1 + i_Size/(w_density*w_size) )
In other words, most of an attack's momentum comes from attack multipliers (like the x2 battle axes get), race size, and strength. Meaning that barring extreme circumstances or extremely small individuals, momentum increase from density is small.
It's worth noting that for a blunt attack to not be deflected, a weapon's material must have sufficient impact yield. However, since war hammers and maces have small contact area, this shouldn't be a problem. A platinum war hammer or mace should have almost three times the necessary impact yield to bypass this check against copper armor.
The matsci page is pretty dense but very informative, I'd recommend it.
Edit: Forgot to mention that I still appreciate making blunt weapons out of electrum, rose gold, or platinum, if only for cool points. If you wanted a good balance of impact yield and density, then my recommendation would be steel (very high impact yield) or bronze (for a solid mixture of density and IY).