I can only tell you how mine works. I have one from Smoky Lake and I love it. For years I fought getting one and instead did long draws, regulating the flow as best I could to keep the temperature at the exact right temp. I often got draws of 45-75 minutes and tweaked the draw off valve to hold the temp. right. My only issue was if a customer stopped and we got talking, then I lost focus and that's when I had things go south in an instant. Then I got my Smoky Lake Auto draw, the basic "Simplicity" model and it works perfectly. I have a ball valve in the line to regulate the flow, but I don't try to get a constant draw, I regulate it to go just a little faster than needed to hold a continuous draw and I watch the temperature display. I have my draws going into a draw tank. When a draw is finished and the valve closes I check the density to verify, if it's not exact I adjust the valve control, it can be set in 1/10 degree increments, I go up or down as needed. Once I find the perfect setting I only recheck about every 1-1.5 hrs to make sure the barometric pressure has not changed and caused it to need adjusting. The beauty of it is that you can then concentrate on other tasks, the draw will be right.
Likely the Smoky Lake Crescendo might be even better (because it varies the valve opening based on the temperature of the syrup flowing thru it) but I will likely stay with the one I have.