While my favorite big game cartridge is the .30-'06, the truth of the matter is that I have killed more deer in my 33 seasons of deer hunting with the .223 Remington than anything else. I've used the .223 now for 22 consecutive seasons. If it didn't work for me, I would have given up on it a long time ago and I certainly wouldn't continue to use it now. But it does work for me and, in fact, it works rather well on the size class of animals that I shoot with it, which typically range in live weight from 70 to 150 pounds.
Over the span of my use of the .223 as a "deer cartridge," I've used the 64 grain Winchester Power Point, 60 grain Nosler Partition, and 62 grain Barnes TSX bullets. While all three of them work, I much prefer the TSX because I believe its superior penetration opens up more possibilities for shot placement. It is also a tighter grouper out of my Handi Rifle than the other two are.
The TSX bullets have significantly more penetration than the Nosler Partitions do and I believe that they go a long, long way toward bridging the terminal performance gap that used to exist between the .223 and the .243 on small deer and similarly sized game, and am therefore content to keep right on using the .223 as a light game round, where legal to do so. The level of penetration that bullet offers simply opens up a few more possibilities for shot placement.
I can't really say that the Noslers give me anything to complain about, but I think the terminal performance of the TSX is pretty much the pinnicle of what one can expect from a .223 in terms of game taking ability. That being the case, the TSX is what I now rely upon most for taking game with the .223.
-JP