The only difference is 3 DT has replaced the 10 DR from FO3, because I figured if toughness provided identical DR to cyborg in FO3 back when DR was the primary thing, that if DT which replaced it was 3, that I should again make it identical (so it would be just as if the DEVs had decided to include the same perk into NV) so I did. It should also theoretically stack with other DT modifiers in a useful yet non overpowered manner.