Not sure how the Nitecore functions but the Solarforce Skyline has an infinitely variable tailcap. It's very easy to use and it would be awesome if they made one to fit their 6P hosts. Not really sure why we have not seen one yet!!!!
I think the HDS rotary offers the best UI available. Instead of infinitely variable brightness, it utilizes 24 step levels which increases efficiency and provides outputs that are evenly spaced based on how we perceive them. The problem with some selector rings as I understand it, is that 1/2 of the dial is a barely perceivable difference (or 1/2 of the dial looks like the same output).
The JetBeam RRT-0 S2 is an awesome little light that has quickly replaced my Quark AA Tactical. You can go from .003 lumens to around 270 with its infinitely variable control ring.
If your looking for under $60 look at the itp sa2 r5 ($40-50)
I love my Sunwayman V10R ti. $60 is a little under most lights with variable control though. Jetbeam makes a few and Nitecore makes the infilux series of lights with a control ring.
The M10R (Fixed output version of the V10R ) is rated at 55 lumens for 10 hours.