Actually differing masses will accelerate under the sole force of gravity at exactly the same rate. The more massive object will only accelerate faster if there is reasonable air resistance.
Every kilogram of mass is acted upon by gravity (9.8N/kg on our planet). This is 'f'.
F/m=a
10kg(m) x 10 (9.8 simplified) = 100N/10kg(m) = 10m/s/s
100kg x 10 = 1000N/100kg = 10m/s/s
Factor in enough air resistance and time and the more massive object will hit the ground first. Would it in the OP's case? Dunno. Not enough info.