Which one is better?

  def show(conn, _params) do
    invoice_id = get_session(conn, :invoice_id)
    invoice_access_token = get_session(conn, :access_token)
    case [not is_nil(invoice_id), not is_nil(invoice_access_token)] do
      [true, true] -> render_form(conn, invoice_id, invoice_access_token)
      _ -> render_error(conn, _params)
    end
  end

  def show(conn, _params) do
    invoice_id = get_session(conn, :invoice_id)
    invoice_access_token = get_session(conn, :access_token)
    case [invoice_id, invoice_access_token] do
      [invoice_id, invoice_access_token] when is_nil(invoice_id) or is_nil(invoice_access_token)
        -> render_error(conn, _params)
      _ -> render_form(conn, invoice_id, invoice_access_token)
    end
  end