Worker democracy is the characteristic that's most useful. Regarding that, imo there's a good case to be made even to the conservative side of the aisle in favour of unions, as at its best they can drastically reduce the need for strong top-down regulatory legislation in favour of much more specific, granular agreements between workers and employers made from the bottom up. But the power to be able to do that has been crippled (for good reason in some cases! But not all).