Here is why I shoot a 300 win even though I have built several good 7mm's. The current selection of 300 bullets will better retained velocity at distance, and have BC's at or above the most popular 7mm hunting bullets. You named target shooting, the 300 win barrel will still be shooting accurately after the throat starts to go in the 7. Plus you will always spot hits on rocks and steel better with larger bullets. You can get brass almost anywhere as well as ammo for the 300 win. 7STW, not so much. You mentioned Elk, I will always opt for a heavier higher BC bullet for elk and why I shoot a 300 win even after extensive testing with the 7-300 which is very close to a 7 STW. I like a good 7mm, and I like the STW but there is a reason the 7's have never taken over the 300's. They are close in many situations, but when I weigh the results and add in distance the 300 win is still my choice.
Jeff
If you run the long range ballistics between a 300WM and 7STW the STW passes and walks away from the WM at about 800 yards. I think you might want to restate your quote on BCs on 30 Cal over 7mm(284), when comparing apples to apples (bullet weight to bullet weight) the 7mm is quite ahead of the 30 cal, it's not until you get over the 200gr mark on the 30 cal that the BC's really get impressive, and in a 300WM, those heavy bullets aren't moving that fast (in comparison to the 7mm STW) which directly translates to bullet drop and wind drift.
Seeing how hunting is a main concern, the time of flight is another big benefit the STW has over the 300WM, now this doesn't make a big difference until you're past the 700yd range or so. Example, 168gr 300WM SMK leaving the tube at 3150 has a flight time in the 2.2sec range at 1000 yds, a 168 7mm leaving an STW at 3350 (what mine does) hits at 1.4 sec, that almost a full sec ahead of the WM, and we all know how much an animal can do in a 1 sec.
The STW has limitations, it's meant as a speed freak, which means you need to choose your engagement correctly, for the most part, IMO, anything closer than 300-400yds is too close for most bullets moving at those speeds to preform ideally, it needs some space to slow it down some. Some will argue that WM causes more impact energy, and in some cases it does, but the basic physics of mass x velocity = energy will tell you that a bigger bullet moving slower is the same a smaller bullet moving faster.
The 7mm also fights the wind better in the STW for two reasons, 1) smaller cross section. The smaller cross section means there's less surface area for the wind to push against the bullet. 2) Speed, the bullet is exposed to the wind a less amount of time over a given distance moving as fast as the STW is capable of moving it.
The major downfall of the STW is the lack of factory loading, there's plenty out there, but the likelihood of finding it at WalMart in multiple loadings probably isn't going to happen. MOST, not all, STW shooters are reloaders and factory loadings aren't a huge concern to us who reload. But keep up your research on what you want, ultimately it's your weapon system, not mine. There's plenty of information out there and play around with the different ballistic programs and do some comparisons from different loads and shot scenarios you foresee yourself getting into and see which ones meet your requirements and make your choice from there.