Complicated subject. First is the whole issue of what is a weed? Then the question of which is worse for your crops and your soil, bare earth exposed to the elements, or "weeds" competing with your crops?
Some competing plants are really competition and potentially destructive.
Bindweed and other climbing vines can pull down your crop plants. Not so good.
Something like a dandelion, low growing, deep taproot, not going to shade out anything more than a couple of inches tall - it is shading and protecting your soil, holding water in the soil more than competing with other plants for that water. The deep taproot is breaking through compaction layers, pulling up nutrients. The entire
root system is putting exudates into the soil that support the soil biology. In other words, it is a net contributor to the soil food web and overall beneficial for the growth of plants, any plants, in the soil.
I think that low growing plants that cover the ground, but don't shade out our crop plants, are pretty much beneficial. Climbing plants that are going to climb up my crops? Not so much, but even there, we can use corn or sunflowers as support for beans to climb up, so you have to consider your specifics. Fast growing grasses that spread aggressively through rhizomes and grow both dense and tall? If they are out in a pasture, and livestock like them, they are a good thing. If they are coming into my garden beds where I am trying to grow radishes, then they are a problem.
So much depends on context. Whether you use a dead mulch to cover the bare soil or allow a living mulch to develop, I think it very important to have that soil cover. Given a choice of bare ground or weeds, I would lean toward weeds. More life in the soil, cooler soil temperatures, less water loss to evaporation, better water holding capacity in the soil. No benefits to bare earth.