Thanks and your right Epoxy7,
I would like to start some 3 gun matches and/or milshoot ones. The distances would be from close (2-3 feet) to everything in between till about 500yards (target). That's why I was looking at the NF 2.5-10 x 24 NXS or ZEISS Conquest 2.5-8x32 MC.
Your above statement adds a whole new dynamic.
The demands of that nature on your rifle system will mean a compromise in one or the other, and likely put you somewhere in the middle.
I have three 2.5x10 NXS scopes, and would never consider their use in a close-in three gun competition. For a Service Rifle competition going from 100-500m I think they are at the top of the heap.
If I was putting ONE gun (your Sig) and ONE optic to use for all of the above,
I would look for something along the lines of the ACOG TA31RCO-A4CP, or TA31DOC.
The ACOG will be a blessing at the shorter distances (0-200), but be a hinderance at accurate fire on the longer stuff (300-500) due to a bullet drop compensator that has no adjustment. If your ammo works with the BDC, then you are laughing, but by and large, you will need to figure out where they hit at your ranges with your ammo, and would want to keep that ammo consistant.
Or,
The NXS 1-4. A compromise right down the middle of what you want to do.
A handicap at the shorter stuff compared to the ACOG with a DocOptic, but better for 300-500 yard shooting compared to the same ACOG.
In a one-optic race, it would probably be your best bet.
Or,
Elcan Spectre. Advertised as the solution to your prayers. I have not tried one, and am sceptical that all the bugs have been worked out. Be sure to let us all know how it works for you if you decide to go this way...
Or,
The S&B Short Dot. Due to the cost, I really wouldn't consider the S&B unless I was in a field condition where I could not swap optics. If you consider this route, compare it to buying a decent 2.5x10 and an aimpoint or eotech with quality, repeatable mounts for both optics.