Don't use an extruder based on the pretty pictures, or even how many extruders they have designed. Not only could you could say they just haven't yet figured out how to do it right, but you also don't know how many extruders others designed and never released
3mm is not optimal on a delta, the extra thick rod doesn't flex as well, and on a delta, you need that. It also weighs more. It can be done, it's just not as good.
As for extruder, I've run geared, I've run direct... Nothing, and I mean nothing, is as simple as a geared extruder. No muss, no fuss. Plastic gears, especially herringbone are difficult to do, and if you get even a slightly warped herringbone, the side loads can actually destroy not only the extruder, but the bearings as well. I have a graveyard of them.
Geared can nip your fingers (or worse), gears wear out and strip. Direct has no torque and large steps.
3mm is not optimal on a delta, the extra thick rod doesn't flex as well, and on a delta, you need that. It also weighs more. It can be done, it's just not as good.
As for extruder, I've run geared, I've run direct... Nothing, and I mean nothing, is as simple as a geared extruder. No muss, no fuss. Plastic gears, especially herringbone are difficult to do, and if you get even a slightly warped herringbone, the side loads can actually destroy not only the extruder, but the bearings as well. I have a graveyard of them.
Geared can nip your fingers (or worse), gears wear out and strip. Direct has no torque and large steps.