Balenciaga / help! which size should I choose？

hi  everyone~~~long  time  no  c  lor~~~

im  gonna  buy  a  Balenciaga  bag  in  magenta  (anybody  remember  it?  it  is  2005  F/W  colour),  bt  can`t  decide  which  size  2  buy...there  r  2  sizes  available:  da  first  n  da  box.  Could  anyone  give  me  some  suggest——  which  size  could  go  with  the  magenta  the  best???  The  picture  is  followed~~~

The  Box:  http://www.cricketliverpool.co.uk/index.php?main_page=product_info&manufacturers_id=17&products_id=514&zenid=63c16f48175edc46a5cfd4c6e6444824
The  First:  http://www.cricketliverpool.co.uk/index.php?main_page=product_info&manufacturers_id=17&products_id=512&zenid=63c16f48175edc46a5cfd4c6e6444824

thx  a  looooooooot!!!  ^_^