Onions from seed?

I grew from sets this year. 2 very different results. One raised bed was just onions and was in sunshine most of the time, onions are terrific only a few bolted. The other raised bed was slightly shaded but I also was growing cabbage plants in with the. Actually the cabbage plants were there first the onion sets were stuck in afterwards. These onions are much smaller and even more have bolted.

These were grown on their own
   

These are the ones grown with the cabbage 
   

These were grown on their own.