In a vacuum, where there is no air resistance, all objects fall at the same rate regardless of their mass. Therefore, in such a scenario, the value that will be different for the two objects (the hammer and the feather) is:
the upward push of air resistance
In the absence of air, there is no upward push of air resistance acting on either object. However, if you were considering a scenario with air resistance, the feather would experience a greater effect from it compared to the hammer, which would lead to different values for the upward push of air resistance.
All other options (velocity, time to fall, and gravitational attraction) would be the same for both objects when dropped from the same height in a vacuum.