There's no single 'right' answer to this, as the posts so far show. The best weight for the bridge in a given case will depend on what you're making and what you want it to sound like.

The function of the bridge is to tie the strings to the top, and tell them how long they are so they'll know what note to make. It has to be strong enough as a tie-down so that it doesn't break, and stays glued on. It's mass and stiffness serve to define the string length, along with the mass and stiffness of the top. Secondarily, the bridge is the heaviest brace on the top, and one of the stiffest, so it alters the way the top works. You work with these variables to get what you want.

In theory, a string only works right if it's ends are fixed to something that's totally immobile. The problem is that top that doesn't move would not make any sound, so we're automatically violating that condition. Fortunately, there's a range of values of motion for the top that will work well enough to avoid problems. The heavier and stiffer the bridge is, in general, the less motion you'll get for a given top stiffness and weight. On a top that's flexible in the center, such as a scalloped braced Dread, you will probably need a stiffer or heavier bridge to keep from running into 'wolf' note troubles. That ebony bridge of Martin's that weighs 35 grams does the trick there, especially if you add in some more weight for the pins and saddle. On a smaller top that used 'tapered' bracing, which is stiffer in the center, you'd need less mass, and a lighter bridge would do.

Adding mass in the bridge tends, all else equal, to cut down on the power the guitar can produce, but it cuts it down a lot more in the higher frequencies. Putting on a heavier bridge doesn't give more sound in the bass than t a light one does; it gives less. But, by cutting down the treble even more it produces a 'bassier' sound. Sometimes a small difference there can have a big effect. One of my students once got a little carried away in carving her bridge down, and ended up with one that weighed about 20 grams. The resulting sound was too 'bright' for her taste, and we ended up adding a couple of grams by sticking some poster adhesive inside the top as a quick expedient. Later, when we had time to put on more than a simple wash of shellac, the sound improved, and we were able to remove the goo.

Stiffness with low weight has the opposite effect; it cuts bass more than treble. A light bridge will tend to be more 'responsive' than a heavier one.

There is something of a trade-off between power and sustain too. Adding either mass or stiffness with all else equal will tend to reduce the power of the guitar a bit by restricting top motion, but should add sustain by keeping the energy in the strings longer.

For my own steel string guitars, with 'tapered' bracing, I tend to look for the bridge weight to end up around 25 grams, or maybe a bit more. You can fine tune the weight of the system some by using different pins. Plastic ones weigh about 3 grams/set, ebony is about 5, bone closer to 8, and so on. In some cases, as with my student's guitar, a couple of grams can really make a difference.

Years ago I had a test guitar that came out of the chute sounding amazing, it had an ebony bridge that weighed approx 35 grams, I decided to test the lighter bridge theory, the lighter I went the worse the guitar sounded....I ended up putting a heavier bridge back on and the beautiful sound returned. I have found that lighter bridges don't work for me, go figure. FWIW.... I build/brace pretty light as well.

Scalloped or tapered bracing?

Tapered