The biggest problem with the high-magnification, First-Focal Plane (FFP) Low-Power Variable Scopes (LPVS) is the reticle's line size. If you make the reticle lines visible at the 1x setting, chances are that they will be so thick at 10x as to be useless. I find that the Trijicon 1-8x scope suffers from this problem somewhat, with quite thick reticle lines at 8x magnification. The Nightforce 1-8x reticle lines are apparently so thick at 8x that they are borderline unusable.
The easiest way around the problem is to have reticle lines so fine at 1x as to be virtually invisible, meaning that your low-power magnification settings rely upon an illuminated 1 MOA centre Dot. Science says that a 1 MOA is the same size at 10x as it is at 1x, so the illuminated dot itself does not grow in size as the magnification is increased. If I was a betting man, I'd wager that is how they address the problem in the new Vortex 1-10x - by using an ultra-fine reticle with an illuminated 1 MOA centre Dot...