JDK 1.5 vs 1.6 considerations for JBoss Enterprise Application Server

Issue

We have currently standardized on 1.5 for EAP 4.3 and SOA-P 4.3.  WE intend to use 1.6 starting EAP 5. So  my question is, if I am in 4.3 environment what would be the consideration on why I should got ot 1.6 (apart from EOL of 1.5) Will I get any improvements out of the box by going to 1.6.