It is widely considered to be true that flat burrs deliver more clarity and a more transparent flavor profile than conical burrs. The 1st reason is the distribution of your particles, that the highest percentage stays in your target size. The 2nd reason is due to the 1st reason. You get a better extraction in a predictable rate.Like this you can notice floral, fruity and single origin notes.
Conical burrs require less potent engines to grind your coffee, so flat burrs need highrer RPM due to the physics of them that is more difficult to grind coffee on a flat surface. Conical burrs have typically 400-500 RPM but flat burrs are in the range over 1000 RPM.
Conical burrs are quieter (this is a plus in the morning) but slower. Flatt burrs will deliver your coffee grinds quicker but in relatively higher level of noise.
The heat generation is also different between those two and this matters especially for espresso that we are looking for a thinner cut. Conical burrs distribute the heat better cause the surface is bigger.
One more thing we would like to mention here is heat retention. The definition of retention is how much coffee grind stays in your grinder between uses, and is gonna fall in your next cup and not while grinding. In the conical burrs is easier to retain less coffee due to the geometry and the flow the grinds leave the burrs but with new technologies you have less and less retention with flat burrs using technologies like anti-pop-corn technology.
In the single dose grinders one common solution is the chute, but if it doesn´t work well, then you have higher retention.
It is though a misconception that flat burrs will give you always a better and cleaner cup of coffee. Cause the geometry plays a role but there are other parameters that play a role highlighting the barista that will make the coffee for example.
What you need to have in mind, is that the different geometries produce different coffee.
The roasting plays also a very important role. You will see quite often that the ligher the roasting, the more into direction flat burrs you wanna go but if you drink darker roasted coffees the conical burrs are more forgiving. But on the other hand, for a light roasting you do not want to have high heat while grinding and with the conical burrs you have a gentler grinding.
Last but not least durability depends a lot on your maintanance through the years but one thing to have in mind is that the flat burrs are easier to require an alignment due to their geometry. There is higher sensitivity of drifting.
There is not one single reason to choose one grinder. It is definitely a hard job to read a bit and understand how the work but the more important thing is to know what you are looking for and if not, start slow and low and go higher with the prices. Because even visiting places and tasting coffee will not help a lot. In the end the coffee beans you will have home will determine what you get from your coffee grinder.
This is a nice journey and playing is part of the deal and the only way to find what you prefer.
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