Doser vs Doserless

The advantages of the Rancilio Rocky doser model are:

Cleaner operation – Since the ground coffee goes into the doser, there is less splatter of coffee grinds on the countertop.
Less static – The doser allows less static of coffee grinds. This is not to say there is never any static, but there is a lot less complaints of static with the doser model.
Excess coffee grinds – Typically, one can overdose the amount of ground coffee into the basket. You can dump any excess into the top of the doser.

The disadvantages of the Rancilio Rocky doser model are:

Leftover coffee grinds – Since you are not grinding right into a portafilter, the user may grind too much coffee. This leftover coffee could become stale. As a workaround, many customers know for a certain setting that they can grind for so many seconds to achieve just enough ground coffee for a shot or double shot of espresso. Then, all the coffee is dosed out of the doser by pulling the doser level until all the grinds clear. Please note every coffee bean grinds differently at different settings which can impact the grind time. Hence, you will need to experiment with what works best in your situation. Or, customers only put in a certain amount of beans in the bean hopper, grind it all, and then dose it all into the portafilter.
Doser effectiveness – One of the weaknesses of the Rancilio Rocky doser is the vanes that sweep the coffee out of the doser. There are always some leftover grinds and a brush is needed to sweep them out. For more effective sweepers, you would need a higher end grinder (i.e. Macap, Mazzer, etc).
Variable coffee dosage – The Rancilio Rocky Doser model has vanes that compartmentalize the dosage of ground coffee. These typically dose 6.75 grams of coffee only when the doser is half full. When the doser is less than half full, the amount can vary downwards. The normal dose should be 7 grams.

The advantages of the Rancilio Rocky doserless model are,

Grind what you need – If making 1-2 cups every morning (or session), the doserless will cut back on the amount of coffee waste that would accumulate in a doser – especially if one is very fanatical about how freshly ground the coffee must be,
Grinding for other coffee brewing methods – Since the portafilter guide (metal ring below spout where ground coffee exits) is removable, you can place a container underneath. This way you can grind coffee beans for other coffee brewing methods, such as french press, drip, etc. You can store this ground coffee in an airtight container in your refrigerator.

The disadvantages of the Rancilio Rocky doserless model are,

Grind fineness adjustment – You should only change the grind settings while the motor is on and burrs are spinning. If not, the burrs clog up with coffee grinds, and then it is difficult to get a fine grind. This is common for all espresso grinders. On the Rancilio Rocky doserless model, you need three hands to accomplish this. One hand needs to hold the front push button on, a second-hand needs to hold down the step adjustment holder, and the third hand simultaneously needs to rotate the hopper to change the settings. However, you can change the front push button on the doserless model so it does not need to be constantly withheld to keep the grinder running.
Not for entertaining – To have to grind per espresso shot, it takes longer to make multiple espressos. While you are grinding into the portafilter, the portafilter is actually losing a few degrees temperature (which can affect your espresso). A workaround is you can grind all the espresso coffee beans into a container, and use a scoop to get the coffee into the filter basket of the portafilter.
Messy – Doserless coffee grinders tend to be messier since the portafilter can overfill or some grinds get out of the filter basket while grinding.

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