Smaller burr diameter usually means less effort but more time. I quite liked the short crank and slim cylinder on the Aergrind - more ergonomic if you ask me. I think Kingrinder K1 is using a similar type of burr. Another thing I liked with Aergrind is that it was still feeding efficiently past espresso (for turkish) while many other grinders will stop feeding or take ages (like Comandante C40). Grind quality is just OK in my opinion though.

My bet is that K0 has the same burr as a whole slew of cheap electric grinders, first seen in Helor 101 ('conventional' burr) and notably a bunch from Timemore like C2. Good grind quality, but very slow for espresso. Grind times can be much longer than what Boren writes, depending on things like size of the beans. It's really meant for filter.

I think the 47/48mm burrs strike a better balance speed-effort-quality. Just don't expect to be able to grind very light beans without putting in a decent amount of effort.. But the roasts that are easy to grind are also the ones that tend to taste best for espresso with the majority of conical hand grinders, so it works out in the end

Light roast is a hell on most hand grinders simply because you either have a fast grind but the effort required because of the fast feedrate is tough, the alternative is slower feeding burrs but then you spend minute grinding that is also just tiring. It works best with more medium roast I simply don't care enough to grind espresso on hand grinder with light roast, well not until I get the base for pietro that take 90-120sec for a light roasted bean at setting 1-1.2

OE Pharos (2). I grind 15 grams per shot at about one revolution per gram...less than 30 seconds per shot.

And horrible in use, the amount of torque needed to grind espresso ain't particularly fun, those burrs really need gear reduction, one of the issues is the generous feed rate of the burrs making it a H in use. For me it's the perfect example that handgrinders need burrs designed for hand grinding.

I decided to purchase the Kingrinder K1. The grinder is very affordable, virtually no space considerations and is capable. The speed and effort factors were within my expectations and capabilities. These newer hand grinders would not suit everyone, however, they would be a good fit for many. I do a pour over brew with an older hand grinder in the morning and 3-4 espresso's in the afternoon with the K1. With this volume, I am extremely happy with the K1. It is a very handy tool for my needs. I want to thank everyone that participated in this discussion. Without your comments, I probably would not have moved forward in this regard.

I had a Malgut for a while, same burrs as the Pharos, and as long as it was securely attached to a non moving surface, kitchen counter with the included suction cups, I didn't find it hard to use at all. I'd probably still have it if it wasn't impossible to align due to defective manufacturing. It's usually recommend that the Pharos bench dogs or some other method of retention are advised.