In drive ,at a stop everything inside the trans also comes to a stop except the pump (spins whenever the engine is on in drive or neutral) the torque converter is spinning ( turbine inside converter connected to input shaft is stoped.) only thing between the two is fluid = no wear. When shifted to neutral a clutch releases allowing the input shaft to rotate ,reengaging drive causes a clutch to reengage to stop the turbine. This causes some ( very little) wear to the clutch. I’d say most wear will happen to the linkage due to excessive shifting.