There's a little more leeway in wind hold with the 7, but most hunters will never see the difference.
No argument here. I never said that the average hunter will be able to take advantage of the difference, but to say that there is no difference is just not correct.
For example, The 180/7 vs 170/270 will have around 2" difference in wind drift at 500 yards @ 10 mph, which is the difference in hold between a 10 mph wind vs a 12 mph wind. Either will be holding off vitals in those conditions, and I'm of the opinion that if I have to hold off vitals with my wind hold, it's time to get closer or re-position.
The difference is about 3" using 2850 fps for the .270 Win and 2950 fps for the 7 Mag (not red-lining either cartridge), but that's not really the important thing. Comparing wind drift in a simplistic 10mph full value wind is not typically the reality we encounter in the field. We often deal with wind that is constantly gusting, changing directions, etc. If the wind where you're hunting on a given day is gusting between 5-20 mph, suddenly the difference between the two bullets is 6" if you happen to break the trigger during a 20 mph gust. So while 3" in a simple 10 mph FV wind doesn't sound like much, it can be a big deal in the right circumstances. The biggest advantage most guys will see, is the ability to hold on vitals further out without having the bullet pushed off target by an errant wind change or by a wind call that isn't 100% correct. As an example, if we assume an elk's vital zone is 16" across, using the same simple 10 mph constant FV wind, you could hold center vitals and not have your bullet pushed outside of the vital zone by the wind, even if there were let-offs and gusts and direction changes, out to 465 meters with the 180 ELD versus 405 meters with the 170 EOL, assuming sea level atmospherics. So using your criteria of needing to sneak close enough to hold on vitals, you could stop sneaking 60 meters earlier with the 7RM. Again, I'm not saying that the average dude will see the difference, but the advantage is there in the right hands and situations.
The thing that most hunters will be able to differentiate is the recoil - there's a 20%+ increase in recoil with the 7 mag. I've found that portable (say 8 lb or so) 7 Mags aren't much fun to shoot, whereas 270s in the same weight range are a bunch easier to shoot. I've also seen this manifested with a whole bunch of hunters. The 270 guys generally kill stuff without issue. A bunch of the 7 Mag shooters have trouble with the recoil, resulting in missed or wounded game.
I'm a proponent of lower recoil promoting more practice, higher round counts, and greater familiarity with a load's trajectory, but when the recoil difference between two loads becomes minimal (the .270 with 170gr bullets recoils more than grandpa's 130gr load) and the ballistic advantage of one load over another is significant, there comes a point where the reduced recoil isn't yielding a net gain in making hits in varied field conditions. IME, if a guy has trouble making hits with a 7Mag, he will also struggle with a .270. If he has shot enough to become familiar with a .270's trajectory, he's usually conditioned enough to do quite well with a 7Mag. If we're concerned with maximizing the ballistic performance to recoil ratio, then the 6.5 Creedmoor with 147's at 2700 fps looks pretty good. It'll go to 435 meters before the same 10 mph wind pushes the bullet outside of the 16" vital zone.
Either way, my initial comment on the ballistic advantage of the 7Mag over the .270 wasn't about the average hunter, but simply the fact that the advantage exists. A good rifleman can take advantage of that advantage under certain circumstances
To quote Bryan Litz "Regardless of your level of skill in reading wind, choosing equipment with superior ballistics will improve your chances of success in long range shooting".
