In my opinion, there is a definite difference in effect of BDO and GBL/GHB. BDO feels more dirty and makes you cognitively inhibited, while GBL/GHB rather enhances the mental processes. This varies from person to person though.
I heard a rumour that BDO in itselfs might act as a GABA-agonist prior to metabolisation to GHB, is there anyone who knows more about this? If this is the case, it would explain a lot concerning the binge from BDO vs. GBL/GHB.