IS Cluster -VS- OS Cluste


We are running IS4.6 in Windows 2000 Advanced Server. We are at the point to decide whether to do Operating System Cluster or Webmethods IS cluster.

Our application serves http request which is statless i.e we do not care about holding on with a session, in fact we kill the session as soon as a transaction is over. We do not care about retry or checkpoint/restart functionality

I would like to get any suggestion from Gurus, to which way should we go and why?