FWIW I have a personal collection of about 40 one-knob processors I used for songwriting, but these are more complex than just turning a knob to change a parameter. For example with the compressor, turning up the knob lowers the threshold, increases the ratio, makes the knee harder, and adjusts the output to compensate for the changes. So somewhere along that continuum, I can usually find the setting I want in a couple seconds. 

Anderton
FWIW I have a personal collection of about 40 one-knob processors I used for songwriting, but these are more complex than just turning a knob to change a parameter. For example with the compressor, turning up the knob lowers the threshold, increases the ratio, makes the knee harder, and adjusts the output to compensate for the changes. So somewhere along that continuum, I can usually find the setting I want in a couple seconds. 

So what do you think is easier to manage? Having 40 one knob plugins? Or having one plugin with 40 knobs and presets to select?

It's a pressing question for sure. Because ever since the style dials have been introduced, it's been illegal to use anything else. If you fire up any other plug ins, a SWAT team comes bursting through the door, and you're straight off to Guantanamo.

Doktor Avalanche

Anderton
FWIW I have a personal collection of about 40 one-knob processors I used for songwriting, but these are more complex than just turning a knob to change a parameter. For example with the compressor, turning up the knob lowers the threshold, increases the ratio, makes the knee harder, and adjusts the output to compensate for the changes. So somewhere along that continuum, I can usually find the setting I want in a couple seconds. 

So what do you think is easier to manage? Having 40 one knob plugins? Or having one plugin with 40 knobs and presets to select?

When speed is of the essence, definitely 40 of my one-knob plug-ins. They all show up in their own folder in the browser. Drag in, turn knob, done. In the example of the compressor, there's essentially a new preset every 10 degrees or so of knob rotation. Imagine being able to scroll through presets and have them load instantly as soon as they appear instead of selecting, deciding, clicking something else, tweaking a control if it's not quite there, etc. Even better, unlike regular preset selection the "presets" morph seamlessly from one "preset" to another, so you can get "in between the presets" without having to do any programming.
 
Same with my ADT one-knob control. You can think of it as a continuum of instantly-loaded presets. I also have a vocal reverb that's again, basically a collection of presets you sweep through with a single knob...very convenient.
 
The only reason I have 40 of them is because I did a couple and found them so useful I did more. However, many of them are more prosaic and are just for convenience...for example I have a humbucker-to-single-coil converter effect. That could just as easily be a preset with an EQ, however, the one knob rotates through "more of a single coil sound" to "less of a single coil sound" and again, it's controlling multiple parameters simultaneously which would require a considerable amount of tweaking to a standard preset.
 
I have to admit that sometimes I don't replace the single-knob effect with something more sophisticated because it already has the sound I want. Maybe I could obsess over finding something "better," but it's like the story I tell of the VI with 600 kick drums...if you hit kick #23 and it sounds good, you don't really have to keep going through the other 577 kicks to see if you can find something  better.