i'll assume you are talking about s13 sr's:
SR20DE compared to the SR20DET:-no oil squirters-Distributer ignition instead of direct coild on plug-no turbo or turbo support fittings (duh)-higher compression (not turbo freindly)-less stout bottom end-Shorter transmission gears-smaller 270cc injectors-different ECU
NA SR's are still really cool though
NOTE: Dont even think about attempting to swap a FWD USDM SR20 into a 240, it would cost 3 times as much as just buying a JDM RWD sr20de.