i have onions from direct sowing. they’re still quite small (no bulb yet.) had to do plenty of weeding, as it was a newly converted from lawn vegie patch. if you weed just after watering thoroughly, the weeds come out with their roots fairly easily, without disturbing the soil much.
the onions were taking so long to come up that i inter-sowed with carrots. now both are growing.
we’ll see how the onions turn out.
about growing seeds in pots: it provides a more controlled environment. you can more easily (than direct sown) provide better temperature, watering, weeding, and keep pests away. my favorite thing about it though is that you can start off the plants whilst the garden bed is still growing other crops. so not only do you extend the season but also can grow more crops. some people buy seedlings to save time. i prefer growing from seed.