Depends on how you look at it. The fluffy guy will lose more fat doing the same workout and diet for two reasons: One, he simply has more fat to lose. Two, going from a sedentary life to an active one will burn a great deal of fat right off the bat. During the first month, the fluffy guy will lose fat like a mad man. The solid guy is likely dealing with stubborn fat that is a bitch to get rid of.