RE: 4 or 5 inch vanes
5" is better when using extremely heavy arrows and when using larger than normal broadheads or above average 2 blade heads but in general with most of todays setups,4" is preferred and most likely better given the arrow and broadhead selections of most,or the average hunter.
I myself have gone to 3" but I only use them when using mechanicals.I can shoot fixed really well in the yard with them but don't trust 3" and fixed in the field under all hunting conditions.