ArcGIS users should be using Oracle's Data Pump utility and not Oracle's Original Export and Import unless for the specific reasons Oracle's documentation states.
The following excerpt is from Oracle's 10.2 Documentation set, Oracle Database Utilities 10g Release 2 (10.2), chapter 19 Original Export and Import:
"This chapter describes how to use the original Export and Import utilities, invoked with the exp and imp command, respectively. These are called the original Export and Import utilities to differentiate them from the new Oracle Data Pump Export and Import utilities available as of Oracle Database 10g. These new utilities are invoked with the expdp and impdp commands, respectively. In general, Oracle recommends that you use the new Data Pump Export and Import utilities because they support all Oracle Database 10g features. Original Export and Import do not support all Oracle Database 10g features."
Because ArcGIS provides a native spatial type for Oracle, ST_Geometry, it leverages many of the advanced functionality in Oracle. Advanced functionality such as Oracle's extensible object model, domain indexes, extensible optimizer and the ability to define behavior when the type is exported and imported.
To ensure the correct behavior when exporting and importing data, ArcGIS recommends the Oracle Data Pump utility is used and not the Oracle Original Export and Import Utility.