WIND

"Small and Micro diameter arrows have better wind drift resistance!" We've all heard it. Thinner arrows should be able to slip through the air and body smoother. Makes sense...right? 

On the surface, this makes sense. Thinner arrows, less surface area, less interaction with wind and organs. But this really only holds true with  BARE SHAFTS. Once you add vanes to the back of the arrow, everything changes. The truth is, as it pertains to wind drift, that the less air your vanes effect in flight, the less the wind will effect your arrow. Some vanes can cause a wind-tunnel greater than 36 inches wide when combined with the amount the back of the flexes in flight. 

PENETRATION

The argument for penetration is similar to that of wind-drift resistance. Something thin should pass through a medium with less resistance than something thicker. Again, in theory, this makes sense on the surface...but we're forgetting one VERY important piece of information. The arrow is led by your BROADHEAD. In today's day and age, your broadhead can have a cutting diameter anywhere from 7/8 of an inch to 3 inches! With a hole that large, does it REALLY matter if the arrow behind it is .226 (4 mm) or .307 (6.5mm) inches wide? 

Keep in mind that many penetration tests are done either on a target or in ballistic gel. These types of tests certainly have their place, but they're not comparable to passing through tissue. Targets and ballistic gel alike react to the arrow shaft differently than tissue. Consider a foam target. You shoot an arrow into it, that arrow and tip push into the foam, but the foam is gripping around the entire arrow the entire time. (We've all had arrows get stuck in a foam target!) Ballistic gel reacts similarly with a bit less hold. When shooting into organs and tissue, however, the broadhead cuts a gaping hole which loosens the grip on the arrow as it passes through. 

So what does this all mean? Simply put, thinner isn't inherently better. And, when paird with some of the other information from the .166 and .204 section, you may be giving up way more than you're gaining when going form a fatter arrow to a thinner one.