SLES was great until their parent company (Novell) went bankrupt, so much smoother than RH. Great driver support and high end system integration (HA, big NFS). But there were always packaging difficulties because there was a huge delay between releases. Just never had enough engineers to keep up with other systems.

Novell isn't their parent company anymore. Hasn't been since 2006 when Novell was bought by Attachmate. Attachmate then got bought by Microfocus which absorbed Attachmate, NetIQ, and Novell. SUSE survived and is an independent business unit. SLES 12 is solid.

Attachmate staved them of capital. Many of the best engineers left, e.g. for Red Hat. SLES has improved a little of late, but still far behind.

If you can do your post-install configuration at the command-line (as a script), kickstart works well. I've done that in a few places. The PXE support for kickstart scripts is nice too.