Windows 2003 Vs Red Hat Linux Vs HP UNIX

Please can any body tell me in Detail the pros and cons of these server because I am sick of using WebMethods Server on Windows. Actually I am using two WebMethods Server in clustered environmaent and there are so many application using its services. I am using load balancer to transfer and execute services depends upon the health of server but still I found lot of performance issue sometimes one took 1 hour n sometimes it took more than 2 hours and I also veryfied that all the required parameters are same. So many time I have to restart the server. I heard that Linux/Unix has much better performance than windows.I m also planning to use LDAP . So can you please let me know in Detail the pros n cons.