User using as_json vs active_model_serialization

using active_model_serialization

def show
  respond_with User.find(params[:id])  
end

def create
  user = User.new(user_params)
  if user.save
    render json: user, status: :created, location: [:api, user]
  else
    render json: { errors: user.errors }, status: :unprocessable_entity
  end
end

def update
  user = current_user
  if user.update_attributes(user_params)
    render json: user, status: :ok, location: [:api, user]
  else
    render json: { errors: user.errors }, status: :unprocessable_entity
  end
end

using as_json

def show
  user = User.find(params[:id])
  render json: user.as_json(only: [:id,:email])   
end

def create
  user = User.new(user_params)
  if user.save
    render json: user.as_json(only: [:id,:email]), status: :created, location: [:api, user]
  else
    render json: { errors: user.errors }, status: :unprocessable_entity
  end
end

def update
  user = current_user
  if user.update_attributes(user_params)
    render json: user.as_json(only: [:id,:email]), status: :ok, location: [:api, user]
  else
    render json: { errors: user.errors }, status: :unprocessable_entity
  end
end