Direct drive bowden?

I've been looking closely at ultimaker's bowden and doing some cursory research into other bowden systems that have been developed in the RepRap community. I'm curious why ultimaker is using that big gear to step their motor down. I've also notice d the gear stepper extruder used with the Huxley. Is that much more torque really needed? I have definitely seen designs that use steppers for direct drive and I would think direct drive would be the preferred option [1], given the flex in the bowden cable. Did these extruders just not prove viable?

I have one of makerbot's custom, high torque NEMA 17 motors, as well as s bunch of standard NEMA 23s (from my old, defunct Darwin.) Is there any consensus or good rule of thumb that's emerged for how much torque is needed for bowdens?

[1] [www.thingiverse.com]

L

One thing to consider is the volume of plastic per step. I my self have designed an extruder with 10.89:1 gearing so I can print object with very small layer heights combined with short moves. A direct drive extruders single step is is enough plastic to draw a 0.1mm layer 5mm long which does not allow you to print highly detailed models (tiny details).

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I have been wondering about this too.
Will not microstepping help this by a factor of 8 or 16?

I do use 16x microstepping and when trying to print the Yoda from thingiverse at 50% size and sliced at 0.04mm (40 micron) more than 90% of the moves are less than one step using a Gregs extruder with stock gears.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Thanks Sublime.
Since I want good resolution it looks like geared is the waay to go.