Why the two releases so close in time? The OCI8 extension is one of the few extensions that has a dual identity, being in both the PHP bundle and in the PECL repository. OCI8 1.4.2 contains the same code as in the recent PHP 5.3.3 release. The PECL bundle was made for anyone who wants a PHP 5.5.3-identical version of OCI8 when installing via PECL.
He describes some of the bugfixes that comes with this release (and what specific circumstances if effects) as well as the requirements you'll need to be able to upgrade to this new version.