"My answer is that those requirements pretty much
narrow it down to Novell and SLED (SUSE Linux Enterprise Desktop).
Novell, and its resellers, knows support and SMB.
"In particular, if I don't really know Linux that well and I'm
running an SMB I want a company that can offer me the full support
package. That's more than just 24x7 phone support. Both Canonical
and Novell offer that. Novell also offers other support options
such as certification, training, consulting, and even retaining the
services of an engineer."