When there are no preferences at all, Condor gives out matches in no
defined order. (And we'll never put anything by default in, because we
have no idea what's best. Should we prefer fast machines to slow machines?
Should we prefer "dedicated" to "desktop" machines? More RAM versus
less RAM? Too many options...)
Instead, we punted to the user. Check out NEGOTIATOR_PRE_JOB_RANK:
http://www.cs.wisc.edu/condor/manual/v6.7/3_3Configuration.html#SECTION004316000000000000000
It lets you sort the list of machines that a job matches with.