I'm assuming you're comparing two aircraft of the same type at different weights. I'm also assuming that the deceleration is in level flight and that engine thrust at idle is negligible.
Then it depends. The retarding force F is the drag. At high speed the drag is mainly parasitic (i.e. the drag due to lift is small in comparison) and the drag for both aircraft at the same speed is about the same. Then from A=F/M follows that the deceleration of the heavier aircraft will be less than that of the lighter aircraft.
However, if both aircraft are flying at their 'green dot' speed (where drag due to lift is of the same order as the parasitic drag), both aircraft have the same lift/drag ratio and decelerate at the same rate.
Last edited by HazelNuts39; 21st Nov 2012 at 16:11.