in-list iterator is supposed to be faster, more advanced
I'd be interested in seeing the documentation link for that.

Code:
SQL> SELECT dummy FROM dual WHERE dummy IN ('a','b','c')
  2  
SQL> @xplan


--------------------------------------------------------------------
| Id  | Operation            |  Name       | Rows  | Bytes | Cost  |
--------------------------------------------------------------------
|   0 | SELECT STATEMENT     |             |       |       |       |
|*  1 |  TABLE ACCESS FULL   | DUAL        |       |       |       |
--------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("DUAL"."DUMMY"='a' OR "DUAL"."DUMMY"='b' OR "DUAL".
              "DUMMY"='c')