Admittedly, I look for little gains because of the rule restrictions. But the small block step headers appear to work well in mild as well as some race combos as shown by my examples. They also have the advantage of thicker materials, eliminate the need for a 90* oil filter adapter, have no issues with speed bumps and mini-starters aren't difficult to remove & replace. Inner & outer coatings also need to be factored into the comparison.
But true, they aren't for everyone. Many feel the advantages are worth it and they are made in the USA. But there will be issues with any product for whatever reason. Can't comment on their bigger headers because I never needed them. To each, his own.