I'm a user of Debian but can see why some people prefer Redhat, and I've used it myself.

Perhaps the main difference is that there is more official vendor support for Redhat i.e. device driver RPM's etc. This could be something like an LSI RAID card perhaps, or a filesystem like Stornext. I know you can often find community built software/drivers for Debian but some organisations and people prefer an "official" source.