XFS - Custom Kernel or Module?

Hey everyone.
I am going to be using XFS for a project coming up. We're running RHEL 5.5. Simply typing

modprobe xfs

works just fine. The kernel module loads without any issue. Is there any issue with doing this and inserting "modprobe xfs" into /etc/rc.modules?

Is there a major reason to compile a custom kernel instead? I'm trying to find some more information. Any help would be very much appreciated. Thanks!