depends on the configuration you have, if you use rac oci the is the best option is to use high availability and load balancing, with the option TAF. oci also lets you set up connections through ldap. for performance, C is always more efficient than java.
There is no one product.
You can/should connect to Oracle via the Oracle thin driver.
You can/should connect to MySQL via the driver supplied by MySQL.
And that assumes you are connecting from Java. Avoid C code
if at all possible in that case. There is typically nowadays no difference
in performance, and C code bugs can kill a JVM and C libraries have
a brittle relationship with the Java portion of the driver and if you
misconfigure or mismatch you can get inscrutable failures.