Matter of personal preference. The helical will stabilize quicker from a bad release .You should make sure you have the proper shafts for your bow from the get-go. After that, the fletching will just help it shoot "better" with more consistency. The bigger the fletch or more twist or greater number will increase drag and slow the arrow and minimise any wobble. The straight fletch preferred by some wheely guys ,is usually in response to the arrow rest clearances. When using feathers, the arrow will still spin in flight with a straight fletch, because of the structure of it.