From what I understand both the LotusScript interpreter and JVM sit on top of
the Domino native code. This means that when you call something like
getFirsttDocument() in either language, the actual binary code that gets
executed is the same in both languages. Asuming the interpreter/JVM overhead is
the same - then there should be no performance difference between the two.
The single reason I use predominantly LS is that the knowledge pool is deeper,
ie: currently more people know LS(aka VB) than do Java. This may change in the
future. From a support perspective this makes maintenance easier for others.
My pet hate is that LS is *NOT* a true object oriented language. It is
basically structures with functions. Inheritance, overloading are the big two I
feel are missing. This can make you LS code much less elegant than it could be
in, say, Java.
My rule is: If you're doing simple stuff (getting and saving documents, etc),
use LS. If you want to do something a bit more difficult that you cannot do
without mangling your LS code, use Java.