I don't think I qualify as an expert, but I do have extensive experience with the Leupold and Nightforce scopes both as a PD sniper and a former military sniper.
Leupold mark 4 - excellent scope, I never had any problems with these scopes and I used them for years.
Leupold VX-III - I actually had a reticle start to slip on me. After every shot, the reticle would slip clockwise. The scope was mounted on farely heavy .308 win.
Nightforce NXS - I've been using one for the last 4 1/2 years. I shoot weekly and I will tell you that this scope is the best I have ever used.
Schmidt & Bender - I've only looked through them, but I know their reputation is top of the line glass.
One of these days, I'm going to have Kirby build a rifle for me and it will have either a Nightforce or a Schmidt & Bender on it. I learned long ago that trying to save money on equipment rarely ever saves you money....ie, buy the best the 1st time and be done with.