I voted for the Burris Fullfield II. Honestly though, I think the Bushnell Elite 4200 is better in terms of glass quality, but nothing else and it's not a very big glass quality difference. The adjustments on it are the same ones as on the 3200 series, which are something I'd expect on a $30 scope. The ones I've used haven't tracked well at all, haven't been repeatable, and all in all are just lousy. However, if it's a scope that you will zero and not mess with again, you should be fine as once zeroed they seem to hold zero.
The next issue with the Bushnell to me is the crappy customer service they have. It seems like for every story I hear of someone having a good experience with Bushnell's customer service, I hear about 5 stories where people sent their scope in for warranty work only to have Bushnell tell them it has a bent tube, or some other fault that the owner caused, and offer to sell them a new one at a "discounted" rate. Their CS is the biggest thing that would keep me from recommending them.
That said, the Vortex Diamondback is also a great choice, or even better the Viper scopes you can get on clearance if you can live with one of the sizes on clearance. They also have great customer service to go with their great products. It to me would be very close between this and the Burris FFII as the way to go with a scope in this price range.
As for the Nikon Prostaff, I've not used any of the newest ones so I can't say to much about it. However, I've used the older ones and it seemed like a solid scope durability wise, the glass quality left a lot to be desired. While it was decent and would probably work okay for 98% of the hunting situations people would get into in legal hunting hours it was just a big step down from the Burris, especially in low light. The turrets were also lacking on these older Prostaffs. To me in the price range of the FFII and the Diamondback it wasn't a good deal, but at the $100 price range you could get them on clearance for, it was a great deal for a solid scope.
That said the newer ones have better turrets and are supposed to have better glass, I just haven't gotten to test one out yet.
I do have a couple of Monarchs, and while I like the turrets better than the Prostaff by quite a bit, and even quite a bit better than the regular turrets on the FFII, and the Monarchs do seem like a tough scope, but I really don't see much of a difference at all in glass quality between and the older Prostaffs. I think the FFII has better glass than even the Monarch, but the Monarch does seem to be a pretty decent scope.
I don't have much experience with the Redfield, but it seems to be similar glass wise to the VX-I's, which I've also had experience with several of. To me the biggest issue with the VX-I is the durability doesn't seem to be there. I've had 2 of them fail, and the 3rd one I didn't use. A friend also bought one and his also failed to hold zero right out of the box. Mine at least worked well for a bit before failing to hold zero. One of mine failed twice. Leupolds warranty is nice, but it's not something I want to keep having to use.
The next issue is the friction adjustments. They are absolutely horrible. They aren't accurate at all, and are just a pain.
I know the Redfield has click adjustments so it should fix this issue.
The next issue is the glass. While it's decent, and they certainly are worse scopes out there, it's not in the same class as many other scopes in that price range. The Burris FFII blows it out of the water especially in low light. Heck, I have compared them to 2 cheaper Simmons and in the day I couldn't tell a difference in glass quality at all, and in low light the Simmons were slightly better. The glass quality just isn't great, but I've compared them to others like Bushnell Banners, etc, and the Banners are certainly worse. I just don't see the reason to spend this much on a scope with this kind of glass, when you could get the Burris or Vortex and be getting glass quality that is a ton better. The Redfield has similar glass or so it seems, and I feel the same way about it because of that. I've also heard several reports of the Redfield changing the poi with magnification changes, but they were early on and I haven't heard of any of these reports lately so I hope that's worked out.
I've also used one of the Center Point 4-16x40's and while it tracked well which surprised me for the price, and it always held zero, the glass quality was not anything special at all. It was in no way comparable to any of the scopes on that list. At lower powers it looked decent. Not great, but certainly decent and I'd feel fine in most hunting situations with it, but on higher powers the glass deteriorated quickly. It looked just washed out. It was a decent scope for $70, but even the Leupold VX-I blew it away glass wise.
That being said, I've found very few modern day scopes that I couldn't see with at the last of the legal hunting hours. While there have been one or two, there haven't been many. Some have been better than others, but lets face it you don't really need a S&B to make it to the end of legal hunting hours. I think a lot of people get too wrapped up in trying to push the limit or see slightly after legal hours. However, I do like to get the best glass possible for the money.
All in all, I just feel like the Vortex or Burris is the best in this price range from what I've used.
