I have 2 very similar basses. One is a 70's Ibanez Challenger lawsuit P-bass, and I recently got an early 80's Ibanez Blazer, which is basically a post-lawsuit Son-of-Challenger. Besides the cosmetic differences, the biggest difference was the bridges. The Challenger's is Fender-like -- lightweight stamped steel. The Blazer's bridge was an enormous hunk of machined brass. Sitting in my lap, they felt identical. But when played, the Blazer was much deader. So I swapped out the bridge for a Fender one, and voila! Cured! I've never owned another bass with a big brass bridge, but you see them all the time, and the bridge is often a big selling point. But I wonder... do they help or hurt? In the case of Ibanez, all I can figure is that it was a misguided attempt at "value-added." These two basses, by the way, while not especially slick players, are the most rock-solid, manly basses I've ever recorded with.
Seems like I read something awhile ago about brass bridges emphasizing lows more while aluminum/steel bridges emphasize mids more. I wouldn't say one is necessarily better than the other, just that they serve different purposes.