It's a common scenario to have weblogic hosted apps connect to Oracle RAC in the backend. From weblogic perspective, there are two ways to connect to Oracle RAC.
1)   Use WebLogic Multipool:   This would mean all the failover/loadbalancing of JDBC calls will be taken care by weblogic JDBC framework - built within application server.
2)   Connect-time failover :   This would mean, all failover/loadbalancing of jdbc calls will be taken care by Oracle driver.
Now what is better approach?   Based on testing and feedback from Oracle, multipool approach is a better choice.
In case of connect-time failover scenario, failover can take lot of time (max would depend on tcp timeout).
Oracle FCF (fast connection failover) would help to some extent in reducing the failover time, but still the failover would be connection by connection instead of whole pool atonce.
Failover in case of multipool is faster compared to FastConnection Failover feature from Oracle DB.
Also, XA connections are better taken care of w.r.t multipools since weblogic framework would make sure all JDBC calls within an XA transaction would reach the same Oracle server.(which is not the case with Oracle thin driver)