It seems like you guys are trying to make a "gray area" into a black and white situation.

Will an outside force affect a bullets trajectory? Heck yeah. But that doesn't stop at brush that includes wind, rain etc. etc. So obviously a bullet affected by an outside force will not perform EXACTLY like it would have had it not been altered.

BUT what you are missing is HOW MUCH?

Yes both a .223 and a .308 will be affected by brush or wind or whatever but the .308 will be affected LESS. If the .308 moves an inch and a .223 moved 5 inches the .308 would be a much better choice.

So obviously there is no "magic" brush buster but a heavier bullet will be effected LESS in any situation involving wind brush or whatever.

Now it is also obvious that one would want to take the cleanest shot possible but it would be easy to miss a twig or branch or wind gust between you and the deer. So in all these situations your best bet would be a heavier bullet.