I have used and enjoyed my Mahlkonig K30 Vario for 4-1/2 years and their ProM before that. So it has been about a decade since I had any experience using any grinder but a Mahlkonig. So, this is not an attempt to compare any other brands of grinders. Also I do not "weigh and grind." These Mahlkonigs were not designed for that kind of single dosing. I usually put a small load in the hopper and then grind by timer. So this is also not a comparison with any single dose machine.
But I assume many people will be wondering if the E65S is worth the $350 price bump over the K30. I had a chance to work with the E65S at this month's Boston Expo, and decided to buy one, since it has finally won NSF certification and is finally available in the U.S. in a 110v model with a smaller consumer hopper. I have had it for several days now and have a few observations.
1. As anyone can see online, the E65S has a much smaller footprint, which allows more breathing room on my tight bar space.
2. Then, going roughly top to bottom, the hopper is sturdier and locks firmly into the body. Instead of being hinged, the hopper lid just lifts off for filling, allowing easier access, if it is partly under cabinets, as mine is.
3. The top collar of the machine adjusts the fineness, as it does on the K30. The E65S collar rotates smoothly and locks down with a simple dial switch on the back, instead of a screw on top.
4. The timer is much easier to adjust on the E65S. A single dial button rotates among several preset times, each of which is adjustable. Adjusting the time on the K30 is tricky, as it quickly moves past the time you want, and you usually have to go back and forth a bit to set it. On the E65S you simply push the button in, and it advances .05 seconds for each soft click as you rotate the dial. You push it in again to stop the adjustment (or it will do so on its own, if left alone for a few seconds). [CORRECTION: You have to push it a second time to confirm the change.]
5. The portafilter holder on the E65S has been grooved out at the back to accommodate the tamping foot that La Marzocco added to their portafilters a couple of years ago. I had to remove the bottom of the holder entirely on the K30 to use an LM portafilter and then hold the portafilter manually during grinds (admittedly not a big burden for under 4 seconds).
6. The E65S grounds are clump-free and extremely fluffy, which I think is partly due to the short path down the redesigned chute and the new, improved de-clumping and anti-static flap. The flap removes easily for cleaning. There is very little retention of grounds, and I have abandoned my habit of a short purge each morning (which, of course, saves coffee).
7. That new chute slides out easily for cleaning.
8. The plastic spill tray is held in place by magnets, which means I can gently remove it for cleaning without fear of jerking grounds onto the counter.
9. The E65S grinds more quietly than the K30, which was already a very quiet machine.
So, to sum up, although the E65S burr set is the same as the K30's, this is a seriously re-thought and improved grinder.
Note: I'm not a tech guy, so please don't ask for particle analysis or a disassembled view of the innards!