A longer stiffer spined arrow would tend to weigh more, have the ability to be arranged for more weight forward of center, have the ability to stabilize better, even with less feather, and keeps the broadhead away from your hand on full draw.
A shorter weaker spined arrow would tend to weigh less, would tend to be easier to handle in general, all as described above.
Of course, if you ever watched the Wensels video (I think it was) "Hunting October Whitetails", a very very very long arrow helps with aiming.
CHuckC