Both are very good. It basically will come down to your preferance.
Barns & Noble have quite a few books on both linux flavors.
The company web sites for each have a lot of information on them as well and that is probly the best place to start.
Suse is now owned by Novel where as Red Hat is still independant but has a lot of backing from companies such as IBM.
Suse is know for it’s customization scripts to setup a server the best way for what you want it to be done. Red Hat you have to make all the tweaks yourself.
These are just a few thought that I have on the subject that may influence you on your decicion.