It's not all that important, but you could indeed choose "Fedora Core": mainly, probably, the various options allocate the right memory for the VM, above all.
For Fedora, you should have at least 256 MB for the virtual machine: but 512 MB is maybe better, at least during the install.
Tha main problem with Parallels, sofar, is that its Linux virtual machine additions - see subsequent X11 problems, etc. - aren't as compatible as they should be: maybe it would be better to wait for a future update, on this front...