Dean, it's less a south north divide, and more a type of league divide like Ric says.
From what I can establish, the saturday leagues are generally the highest standard, but the courses allow more speed and consistent flow, being generally grassy laps of parks.
Our sunday leagues are more of a challenge to hit a consistent pace, as they can almost resemble obstacle courses. Branches, trees/roots, bogs, water jumps etc, on top of the obligatory mud.
You can race our series in spikes, people certainly do, but on some courses, you risk smashing your knees to bits as they have sections of rock hard trail!
As for Sunday being cancelled, in fairness only about 2 races have been cancelled in the last few years, and that's been when really heavy snow has fallen, and the roads have been trecherous.
Anyone who thinks that scenario is in anyway "perfect xc" fare, has more bravado then sense!