I've not had personal experience with the Fenix headband, but in my view it should be the best choice out of the group for standard flashlights (as long as they can fit the narrow adjustment range of the mounts) that are used at close range, where the vertical angle adjustment would come in handy. Its main disadvantages are cost and bulk in comparison to simpler headbands.
I own and have experience with using the Nite Ize headband, which I think works great specifically with ZebraLight headlamps (or any other right-angle flashlight), since you can adjust their vertical angle simply by rotating them in the elastic loop (and they'd be horizontally centered). The loop is really durable and stable for what it is, as is the headband, which is not elastic but stays put very well when adjusted properly (running with it is not a problem). When used with regular flashlights, it's limited for up-close use because the holder is fixed, although it works OK for viewing things at a distance. Its other advantages are that it takes a fairly wide range of compact flashlights, including inline AAAs in the smaller inner loop (there are two elastic loops, one inside the other), and it's dirt-cheap despite being made in the USA. A potential disadvantage is that there is no cushioning between the holder and one's head, which some people have said causes discomfort from the flashlight body protruding inward, while others don't feel any discomfort whatsoever (I'm part of the latter group). In my opinion, every ZebraLight headlamp owner should get one because it's way better than the pitiful headband that ZebraLight provides. :shakehead
As for the Klarus headband, I've neither seen it in action nor heard much feedback about it, but it looks like it has some of the same characteristics as the Nite Ize headband. The main difference is that it's an elastic headband, so while I have no real way of knowing, I suspect that it would not be as stable without a top strap.
And as for the NITECORE headband, it looks like a bulkier but probably more stable version of the Klarus headband, and has three elastic holders (for comparison the Fenix headband has two rotating plastic holders). I guess you could adjust the vertical angle of the top flashlight by moving it back and forth (and it would be horizontally centered), but it would be nice to get some firsthand feedback on how well this works in practice.