From my experience and testing LS agents are always faster than Java agents.
Multithreading is only useful where slow I/O processes are involved such as in
this example. For most agents multithreading will slow things down. Rather than
go to all the bother of writing a multithreaded java agent I would write
multiple LS agents. This requires increasing the number of concurrent agents
the server willl run in the server document.
Regarding LS and OO although not integrated as well as in Java LotusScript does
have OO extensions i.e. you can create your own classes and then extend them
for more specalised requirements.
Finally the real benefit of Java probably comes when used as servlets rather
than agents putting a much lower overhead on the server.