I'm new to growing onions from seed this year. There's a lot of effort involved compared with sets and a long growing period. Personally, I don't think I would put that effort in and dedicate space without knowing what the seed was. Once my Ailsa Craig have done their thing this year, I will however be saving a couple of the best to let them flower for future seed.
I'm at present experimenting with some unknown sweet pepper seeds and they aren't looking too good at all compared to the other known pepper seed I am using this year, probably a waste of time. One never knows if these seeds are FI/hybrid sort of thing that can go a bit pear shaped.