ABAP then Java Add-In vs. ABAP then JAVA

I would like to install the NW04 ABAP and JAVA stacks on the same windows host, using the same maxdb database. It seems that I need to run sapinst more than once. First, to install the ABAP system, and then to install either the Java Add-in for ABAP or a JAVA system. Which option should I choose, the Java Add-in or Java System when I run sapinst after installing ABAP? What is the difference in the choices?