i see nothing but advantages for using a 4x4" fletched arrow.
for the very most part, at sane hunting shot distances, there won't be any perceived flight or speed differences 'tween well made 3x5" or 4x4" fletched arrows.
all my arrows (carbon and wood) sport lw 4x4" 75x105 low profile banana fletches with just a few degrees of offset and no helical. better clearance than the bigger 5" fletchings, quiet, fast, no nock or cock index required (a real good advantage, imo), and you can chop or burn a complete set of fletches for one arrow from 2 full length feathers as opposed to needing 3 full length feathers for a 3 fletch arrow = economical.