There is no difference for a Competitor.

In either a Championship or a Challenge there is an outright winner, 2nd, 3rd and so on per race. Each race has awards for 1st, 2nd and 3rd. A table of race finishes displays each drivers finishing positions on a per race basis.

By Definition in the MSA Blue Book, regulation J3.1.1.1 states:

"Championship - an event or series of events organised for the purpose of establishing the right to an individual for collective title. Such a competition may also be referred to by other titles e.g. 'challenge', 'trophy' or a 'series'."