Testing the Sig against the Vortex, I found the Sig gathered light better than the Vortex. Most of my archery game shots have come at dusk and dawn, just as light was fading. I had a cheaper Bushnell that I had primarily used in dog training. It's light gathering was poor at best. Before I upgraded I tried everything from a G7 to a Halo. The Sig got the nod, best bang for the $.
After getting it home, I experimented with measured distances and the sigs ability. I thought, just cuz it gives me a number does not mean it's accurate, especially on non-reflective targets. I was a little surprised and very pleased with the little units accuracy. Only real down side is no tripod tread in the units base.