Waiting for spring means competing against every other seller who had the same idea. A crowded spring market gives buyers more comparables to shop against your specific house, while a fall listing often faces less competition from other sellers even if fewer buyers are actively looking.
The buyers active in September also tend to be more motivated, whether relocating for a new job or trying to close before winter, and a motivated buyer pool can move a sale faster than a larger but more casual spring crowd.
Whether September or spring suits your house depends on its condition and your own timeline, not a fixed calendar rule. Get your hand-reviewed valuation from Joel Dyck.