I shoot both the 80.5s and 90s in F-TR. Anyone telling you there is no difference between the two probably isn't actually shooting both of them. I am, and I can tell you the difference is significant. Past about 500 yd, the 80.5s aren't even in the same league with the 90s if there is much wind at all. Don't get me wrong, there is nothing wrong with the 80.5, it's a fantastic bullet, great precision and very easy to tune. However, its BC is sufficiently lower than that of the 90 VLD that you will never be able to overcome the BC deficit solely by the increased velocity. Not even close. And the difference really starts to show past 500 yd. That doesn't mean you can't do well shooting the 80s, it simply means you will be at a disadvantage in terms of wind resistance against other .223 shooters using the 90s, or .308 shooters using anything from 155s on up. The 90 VLDs will hold their own against .308 bullets up to the 185 gr range, whereas they will also be at a disadvantage against 200+ gr .308 bullets. In either case, the disadvantage increase with the distance.
Your 7-twist barrel will allow you to shoot either one. You could try both and see what your rifle tells you. In the event you decided to go with the 90s for longer distances, the 80.5s could still be a reasonable choice for 300 yd, where the windage difference between the two bullets will be smaller. If you plan to shoot mostly at 300 yd and only on occasion at 600 yd, that wouldn't be a bad way to go, and would only require developing a load with one bullet. However, I personally would go with the 90 VLDs if I wanted to load only one. Nothing at all will be left on table by going that route.
