As many things we debate there has been an on going debate over the 30-06 vs the 300WSM. First they are both very good but I believe one is better and the other is not needed unless you just like being different and trying something new and don't want a 100 plus year old cartridge.
When the 300WSM first came out I decided to get a Browning A-Bolt but waited a while and then took the leap and topped it with a Zeiss Conquest 3-9x40mm.
Good looking rig, felt good in my hands, pretty fat short cartridge with all kinds of promises behind this cartridge in the Magazines and media. So I said to myself, "this ought to be some humdinger of a round especially after I develope a load for my rifle that it really likes.
Well the process started and I began to work up loads some bullets and powder worked well and as expected some did not and then a few loads showed excellent promise. I really tweaked my load an a 165gr bullet was giving me consistent 3/4' - just at a 1/2". Now this took a great deal of powder, time, much less money and moments when I thought I would give up and I am one who has loaded for a long time.
During this time I had broken my chrony and it was not working right so I bought a brand new one and that is when I was absolutely surprised to say the least. When I put factory ammo through my rifle I was not getting the accuracy on a consistent bases as I was getting with my hand loads. But my hand loads on the other hand were not getting near the velocity of the factory load even though I was at the charge limit of the powders I was using to get accuracy.
In short my 30-06 in my Mark V was not only way more accurate over 9 three shot groups than the 300WSM but was faster than my hand loads out of my 300WSM. Not only that my 30-06 hand loads 60gr IMR4350 was doing 3060fps and was right there with the factory ammo of the 300WSM.
The 30-06 is easier to load for, uses less powder to get there and was more accurate and I have many more bullet choices than the 300WSM especially with the heavier bullets. I can find factory ammo for the 30-06 any where ammo is sold and in more variety than colors in a crayon box. I the 300WSM a good cartridge? YES!! Does it really bring something new to the table? NO!!! Does it even fill a vacant space? NO!! Is it better than the 100 plus year old 30-06? NO!!!! Not by any stretch of the imagination.
Some things are just good from the beginning, they always are good, and they improve with time due to technology and the 30-06 is that very cartridge. When you put it in new modern designed rifles with new steel and add the new powders, primers and bullets to choose from the 300WSM really in my opinion (and I said my opinion) is not any thing new nor a replacement of any thing either.