multi core vs multi app

[David Pratt]

I am trying to decide whether it is best to work with multiple apps in a 
 tomcat instance or run a single app with multiple cores. How do these 
options compare in terms of impact on RAM requirements.

Is anyone using the multicore in production to suggest whether it is 
stable enough to use with replication scripts etc. Is there any sort of 
a write up anywhere of how one could perform a search across multiple 
cores within the single app? Not sure about efficiency of something like 
though compared to merging indexes periodically to search across the 
merged index instead. It would seem that a search across multiple cores 
would add slowness even if this is doable. Any advice appreciated. Many 
thanks.

Regards,
David