I'm in the plant them thick at 3" spacing in row and pick for 3 weeks or so crowd. Then yank them out. I plant bush beans in early May and harvest late June to mid July. Then plant a second crop in late July to pick in September to October. In between I have a small 4' wide trellis with pole beans (Emerite this year) that start producing about the time the first bush beans are worn out. I have to battle the Japanese beetles for the pole beans but they don't bother the bush beans much.

I freeze or give away many of the bush beans during the deluge but the pole beans produce just enough to eat fresh a couple times a week.

I plant them in a staggered double row at 6" spacing. After they're spent you can prune them back with a weed whacker or lawnmower set on high, give them a bit of fish emulsion, and they'll regrow for a second yield.

There are a lot of considerations that could go into my answer. How much seed you have; how much space; whether you intend to can, or eat fresh; and whether you intend to succession-crop where the beans will be grown.

Close spacing requires more seed. The yield per plant is lower, but the yield per square foot (or row foot) is maximized. Such a strategy is best where you intend a quick yield for canning, or if the beans will then be pulled to use the space for something else. Alternatively, you could make several smaller plantings in succession, to spread the yield over a longer period.

Two possible downsides I see to close spacing. If bean diseases are prevalent in your area, or if rodents are a frequent problem, both of those situations are exacerbated by close spacing.

Wider spacing produces healthier plants, and a higher yield per plant... so if you have a limited amount of seed, this would be the best option. Beans are remarkably good at branching out to take advantage of extra space. Plants that are widely spaced tend to produce over a longer period, and are more likely to bounce back for a second picking... so the assumed reduction in yield may not be as pronounced as you might think. IMO wide spacing is better suited for picking & eating fresh. I should point out though that if you have the space, succession planting will spread the harvest out even further.

Personally, I am an advocate for wider spacing. My main reasons for that are seed efficiency, healthier seed if seed saving (which I do) and reduction of disease & rodent issues. In the case of beans, wider spacing can also improve pod quality - longer, better filled-out pods. I give away a lot of produce to others, so that improvement in quality is important to me.