Interesting results.
Just put some outs out this fall for cover after seed corn and potatoes. They're up and looking pretty good now. Don't get much nutrient out of them(I don't think) but I like the way it leaves the ground for no tilling corn next year.

I have to agree with you - I like the how the soil is mellowed when planting into fall-seeded oats cover crop. Most times we don't let them get too big.  If they do, they get harvested.  Oats allowed to grow to boot stage, then harvested, makes a very nice seedbed.

I did one year of hairy vetch back when we grew wheat and the corn loved it. Wish I could find a way to get it to grow through standing soybeans then have it as the cover when soys are harvested.......................ever had any experience with that?

Is aerial seeding an option for you?

Do the clovers fix N like the vetch?

Yes.  Research shows it is not quite as much.  However, I have to wonder.... if you get a better stand, does that make up for some of the difference?  So far, I am seeing better stands in clovers(Crimson) than in hairy vetch.  However, it is too early to make a definitive statement on that.