The 223 is gaining popularity in the woods due to the gaining popularity of the AR platform, not due to it somehow being a better deer killer than a 243.
Having shot deer with both, the 243 is the better all-around chambering by quite a bit.
Cheap ammo is the 223's claim to fame do to it's military use, much like 9mm pistol ammo. On game, the 223 couldn't shine the shoe's of the 243.
