Well there is certainly no doubt that you'll get a cleaner shot the higher your shutter speed. But if you look around at aviation photography, of prop or rotor driven, you won't see any with the prop-stopped.
I would say it's more important to get good panning down. Maybe if a helicopter is hovering it isn't necessary. But for most aircraft shooting, you want to pan smoothly with the subject. And don't stop when you press the shutter. Keep moving smoothly.
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