Because of the long-standing fear that continued fragmentation of the OS would eventually render Unix unreliable for business use, vendors are currently working to deliver on the promise to create more standardized versions. Unix, however, remains a competitive market. For all the work being put in to make Unix OSs similar, firms also are trying hard to get a leg up on the competition. Much of that work, however, does not easily fit into check boxes on product spec sheets. Bottom-line measure for many customers are reliability, performance, and ease of use.
Reliability is now generally excellent for most vendors.
Most vendors are generally quite reliable, although relative performance rankings are constantly changing and improving. If they pull it off, we could witness an OS that is the best of both worlds, whether from Red Hat or Redmond. Read more on Unix web hosting.