Range,
The amount of offset and helical are only a couple of the considerations when fletching. Here are a couple more considerations to add to the mix:
Feathers are about 25% the weight of vanes of the same length. Lighter arrow, faster arrow.
Feathers are faster out of the gate, but tend to dropout quicker downrange, more drag coeffient. Feathers have about double the drag of vanes given the same speed.
A severe helical fletch is pretty hard to glue up on fairly skinny shafts.
Just some thoughts
Aim Hard!