Brass density: 8.9 kg/l
Steel density: 7.8 kg/l
Titanium IRC : 4.5 kg/l
Aluminium : 2.7 kg/l
Just to keep the basics in place.
Steel is the stiffest and hardest, followed by titanium. Alu and brass are about the same, except anodized alu, which has an extreme surface hardness (compared to the basic material)
Then to the bottom line: how do they impact sustain, or tone, or whatever such value? Not much. I bet very few, if any, of us will spot the difference in a blind test. An much less an audience in a musical situation...
Its interesting, Aluminum and brass seem to be the two materials that everyone claim have the best tonal properties, but seem to be on the opposite end of the spectrum.
I agree with the second point. the bridge on a cheap basswood epiphone LP of mine started leaning, so I added a top of the line replacement. At home, I can definately tell it sustains better and has better harmonics than my stock Gibson LP in a direct A/B, but in a live band situation noone could probably tell a difference.
So FWIW is the general consensus that Titanium is more or less worthless in musical applications and aluminum and brass are the choice materials?