Clarity, repeatability, speed, built like a tank and very few adjustments. Keep in mind, this is for espresso, one of the most demanding preparation methods, for drip/press/vac pot the difference would be less obvious. The espresso machine you use makes a difference as well. Using a Robur on a Krups steam toy verses a LaMarzocco FB80 would nullify most of its benefits. My machine is a Elektra 60’s A3 which produces an uncannily clean cup.
Elektra works some magic with their machines, I have used the A3, MicroCasa leva and Semiautomatica, and they all produce some of the best shots out there. I also have a two group Faema I restored, two Gagga lever machines and a VBM Domobar Super, then there is the hottop roaster and pounds and pounds of greens for blending and roasting. Yup, I take my coffee pretty seriously. I have a VBM Doubledomo coming for a buyers guide around the end of this month. Their prototype and gen one machine had a couple of issues. VBM is doing some redesign work and shipping us (team HB) a new gen two for testing, but that is getting a bit off topic.
If you want the big explanation might I recommend you read through…
Titan Grinder Project
Titan Grinder Project: Can it Beat the Mazzer Robur?
If you really want to go over the top we also ran a grind partical analysis with a
Laser Diffraction Particle Size Analyzer and a
Scanning Electron Microscope. Ya, we take coffee seriously.
My house, most of those grinders are for testing.