Delphi 2009 string type performance benchmark

This code was run on a Intel Core 2 laptop, and shows the difference in performance very well. Compiler options used: Code optimization disabled, all checks on.

procedure TForm3.Button3Click(Sender: TObject);
var
  a:ansistring;
  r:rawbytestring;
  u:string;
  w:widestring;
  i:integer;
  s:shortstring;
  c:char; // widechar
  ac:ansichar;
begin
  screen.Cursor:=crHourGlass;
  try
    // approx. 222 million iterations per second
    s:='This is a test';
    for i:=0 to 1000000000 do begin
      ac:=s[4];
      s[4]:=s[5];
      s[5]:=ac;
    end;

    // approx. 43 million iterations per second
    a:='This is a test';
    for i:=0 to 1000000000 do begin
      ac:=a[4];
      a[4]:=a[5];
      a[5]:=ac;
    end;

    // approx. 40 million iterations per second
    u:='This is a test';
    for i:=0 to 1000000000 do begin
      c:=u[4];
      u[4]:=u[5];
      u[5]:=c;
    end;

    // approx. 71 million iterations per second
    w:='This is a test';
    for i:=0 to 1000000000 do begin
      c:=w[4];
      w[4]:=w[5];
      w[5]:=c;
    end;

    // ****************************

    // approx. 40 million iterations per second
    for i:=0 to 100000000 do begin
      u:='This is € test';
    end;

    // approx. 5.5 million iterations per second
    for i:=0 to 100000000 do begin
      a:='This is € test';
      u:=a;
    end;

    // approx. 5.5 million iterations per second
    for i:=0 to 100000000 do begin
      u:='This is € test';
      a:=u;
    end;

    // approx. 3.7 million iterations per second
    for i:=0 to 100000000 do begin
      u:='This is € test';
      w:=u;
    end;

    // ****************************

    // approx. 3.7 million iterations per second
    s:='';
    for i:=0 to 100000000 do begin
      s:=copy(s+' ',1,50);
    end;

    // approx. 4.2 million iterations per second
    a:='';
    for i:=0 to 100000000 do begin
      a:=copy(a+' ',1,50);
    end;

    // approx. 2.5 million iterations per second
    u:='';
    for i:=0 to 100000000 do begin
      u:=copy(u+' ',1,50);
    end;

    // approx. 1.6 million iterations per second
    w:='';
    for i:=0 to 10000000 do begin
      w:=copy(w+' ',1,50);
    end;

    // ****************************

    // approx. 25 million iterations per second
    r:='';
    for i:=0 to 100000000 do begin
      r:=r+' ';
    end;

    // approx. 25 million iterations per second
    a:='';
    for i:=0 to 100000000 do begin
      a:=a+' ';
    end;

    // approx. 25 million iterations per second
    u:='';
    for i:=0 to 100000000 do begin
      u:=u+' ';
    end;

    // approx. 0.0055 million iterations per second
    w:='';
    for i:=0 to 100000 do begin
      w:=w+' ';
    end;
  finally
    screen.Cursor:=crDefault;
  end;
end;

Conclusion:
* Avoid widestring and shortstring.
* UnicodeString is a huge improvement to WideString.