In my experience RHEL has been better at backporting patches and maintaining a relatively stable kernel. This means that third-party software that targeted it is more likely to work over time. Canonical by comparison is absolutely terrible, and seemingly just blindly imports whatever is thrown over the wall from kernel.org even in their so-called "LTS" versions, and now after running an innocuous "apt-get upgrade" command your frobnitz device no longer works and/or you can't rebuild the driver for your frobnitz device due to incompatible kernel changes.
Some vendors also explicitly detail exactly which distro and versions they support ("RHEL or Centos x.y"), so even if you can get things to work on another distro, a vendor can easily deny your support request with the usual BS line: "that configuration is not supported. Switch back to RHEL x.y or SLES and let us know if you can reproduce the issue! La-la-la have a nice day, buh-bye! phone click".
Some vendors also explicitly detail exactly which distro and versions they support ("RHEL or Centos x.y"), so even if you can get things to work on another distro, a vendor can easily deny your support request with the usual BS line: "that configuration is not supported. Switch back to RHEL x.y or SLES and let us know if you can reproduce the issue! La-la-la have a nice day, buh-bye! phone click".