A .243 is perfect for whitetail, even the elk we've got here in southwestern VA. It's accuracy and shot placement that count, not necessarily caliber. I've heard more than one big game guide say that the the second thing they hate most about some of the clients they book is that they bring a .300 or .338 magnum to camp and they don't know how to shoot it. Any guide would much rather have a client with a rifle of a smaller caliber that they know how to handle over something that just has punch.
However, having said all that, I love my 30-06 :]]
However, having said all that, I love my 30-06 :]]