I start about 10% of my beans in 16-20oz drinking cups/garden soil, indoors. Advantages are reliable germination, earlier germination (2-7 days earlier), and starts being several weeks earlier. With these tall deep cups, I've had not one single problem with 500+ transplants in the last decade.
If weather turns bad (heavy rains/cold) just after outdoor sowing, everything could rot, and you're starting over an additional week later. A second sowing means you're about a month behind transplants.
Disadvantages of starting in cups is the extra labor. But to some of us, it's a labor of
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