The "one powder" mission for the two cartridges in question is a reasonable goal, depending on bullet weights. In fact, the bullet selection might even be the focus.
If you liked 60gr Hornady HP's, and 150 Nosler partitions, for instance, either powder would be just fine, and would have a very wide range of suitability. Of the .223's I've owned, H4895 has been a top accuracy powder in every one, with 50-60gr bullets. The same powder has always been suitable for several '06's, especially with 150/165gr bullets.
At the moment, if you can find either powder, you should get out your wallet.