I have no experience of jumpstart, but I believe it's something more like redhat kickstart,
no? I.e. a system for automated installs with a file containing answers to all the questions
that are usually asked when going through the interactive installer.
cobbler is more like a system for managing kickstarts and pxe boot infrastructure. It has 3
basic types of objects; distros (pxe boot images), profiles (associates a distro with a
specific kickstart file) and finally systems (associates a profile with a MAC and IP address).
So you create a bunch of systems with cobbler, and cobbler can generate a dhcp config (based
on a template you can modify e.g. to include non-cobblerized entries), sets up a tftp server
etc. Then you just PXE boot the systems and they are automatically installed with the profiles
you have specified.