Vortex is the best out of those by a wide margin. Ive never heard of sniper before though. The Vortex Viper line beats beats the Leopould VX and the Nikon Monarch lines on glass, amount of MOA adjustments, and price. Plus your scope is covered under warrenty even if its your fault. dropping it ect
You can find them for cheaper. Right now they are running slow but I can get them cheaper than just about anywhere around. I was able to get a few guys on this site a Vortex for pretty cheap. Just got myself a Viper for half price. Let me know what you are looking for and I will call and see what is available.