The price difference between the 2 is about £200, you obviously know there is little difference between the 2 apart from some neck binding, closed pickups and the model name.
But saying that the Standard does look better, but the 3 pickup custom looks even better, especially with the long maestro/vibrola trem unit.. i think i need a cold shower.

http://cgi.ebay.co.uk/GIBSON-SG-Standard-Black-Ebony-Excellent-Cond_W0QQitemZ150035070037QQihZ005QQcategoryZ33040QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
This should finish on around about £600

http://cgi.ebay.co.uk/GIBSON-SG-SPECIAL-MADE-IN-USA-GREAT-CONDITION_W0QQitemZ330031382615QQihZ014QQcategoryZ33040QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Buy it now £380 which is a very good deal, and if i had the money…