Hi mass bridges are often offered as a premium choice or upgrade option, but that’s not always the case. Here is my opinion on them.
Weight: They are much heavier than regular bent-plate bridges. This is a disadvantage if you want a light bass, but an advantage if you are trying to balance a neck dive or something.
Sustain: They often reduce the string-to-body vibration transfer. Assuming that you want to increase your sustain; this is a disadvantage if you have a high-quality resonant body, but an advantage if you have a non-resonant body which might dampen string vibrations.
Sound: Although it might not be apparent in a busy mix, hi mass bridges might add a metallic, bouncy character to your sound. This is a disadvantage if you are going for a traditional vintage sound, but a “potential” advantage otherwise.
Aesthetics: They are big chunky pieces of metal. This is a disadvantage if you are going for a vintage look, but an advantage if you want a modern, heavy, industrial looking instrument.
Cost: They usually cost more than regular bridges. This is a disadvantage if you are on a budget.
So; in my opinion, a hi mass bridge is not a generic “premium” option – despite their price. They are only “premium” if they serve your personal musical purposes.