I usually use 3-fletch for most of my shooting. Mainly because I'm a cheapskate and feathers cost money. If I was shooting in thick stuff and needed my arrow to stabilize quickly, I'd go 4-fletch. Another reason I might go 4-fletch is a situation like I ran into last summer. I got a bunch of butt-ugly artificial barred feathers and wanted to use them up quickly. I've got a bunch of butt-ugly 4-fletchsmall game arrows.