I have hunted extensively with both cartridges and taken dozens of game animals with both, so here's my reasons for settling on the 300 Wby in the end.
1) If you can shoot the 300 WM well without undue stress or flinching, you can shoot the Wby just as well, the difference in the felt recoil in identical guns is negligible. The 300 RUM which I have also used a fair bit is significantly more however.
2) I found the 300 WM with 180 Parts to be a little short on penetration when the angles are, shall we say less than optimum, on large bodied tough animals like kudu or elk. I found the 300 Wby would equal the velocity and trajectory of the 300 WM 180 gn load I was using and would do it with 200 gn Parts or the new 200 gn ABs I use, and would penetrate significantly more, which is what I wanted.
3) My 300 Wby has a 24" barrel and it still has a 200 fps edge on the identical 300 WM, but what is more important to me is what I stated in the above point, 200s at the same velocity as 180s from the WM.
4) Accuracy of the 2 cartridges is far more dependent on individual rifles and barrels than any inherent accuracy advantage which could be attributed to either cartridge. Both will shoot sub MOA groups in a good, well tuned rifle, which has always proven more than adequate for my hunting needs.
In conclusion, all my work with these 2 cartridges was pre homogenous copper bullets, so my penetration "wants" were much more dependent on sectional density in those days. Given new tougher and deeper penetrating bullets today, my primary reason for going to the Wby may not hold as much advantage as it did then...........However I have not totally succumb to the homogenous bullet "Koolaid" and still prefer my Parts and ABs and yes I have used TSXs and TTSXs with varying degrees of success and failure.
I love my 30 cal magnums whether it be the Win mag, the Wby mag or the RUM and find them to be greatly superior killers than the 7 mags I used previous. One thing I have found in my 45 years as a trophy and local hunter is that game does not always present one with the optimum shot angle or inside 200 mtrs and sometimes the outcome of a very expensive hunt hinges on that one shot. I will take every advantage I can get to make the outcome of that one shot as successful as I can and I find the 300 Wby gives me just a little more advantage in range and terminal ballistics using 200 gn bullets.
Some people say there is no practical difference between these cartridges and for 99% of shots taken on game this is no doubt absolutely true, however I find at least some of my shots on game to fall into that last 1% so I choose to use the Wby.
Although you did not ask about the RUM I'll state my findings here anyway as I did a lot of work with this cartridge years before it was introduced as the RUM or even the Imperial Magnum. It is no doubt superior to both the WM and the Wby mag in both exterior and terminal ballistics, however it is not without a price tag. This cartridge needs a 26" barrel to truly make use of it's expansion ratio and the recoil is significantly higher, to the point of being unpleasant even for seasoned big bore shooters. As velocity and bullet weight go up the recoil does not go up linear, as powder weight, velocity and bullet weight all factor into recoil. Time of recoil has as much to do with felt recoil as the actual energy of "equal and opposite reaction", so to put this differently and in easily understood terms, the RUM when loaded to it's maximum with 200 gn bullets has slightly more muzzle energy than a 458 WM and therefore has roughly the same recoil energy, BUT, this recoil energy is delivered to the shoulder in 1/2 the time frame of the 458, making it much more violent and painful to shoot.........this is just physics gentlemen.
