Speed Setting

Print speed directly affects print quality, print time and layer bonding.

When set at slow speeds, all other variables, such as temperature, extrusion rate and stepper calibration have a lesser effect on overall quality.

Once you start pushing the speed up, minor errors or deviations will start to be more apparent.

For example, if your extrusion rate isn't correctly calibrated, you could get excellant results printing at 40mm/s, but push it up to 90mm/s and you'll start noticing spotted infills, or layers not bonding properly, and your print starts cracking along those weak seams.

There is no real way of doing a full calibration with the stock XYZ software or firmware, so just go with the speed you want. When I was still on stock, I don't think I noticed much difference in print speed or quality between the 3 speed options they give (slow, medium, fast)

But if you stick on a custom firmware, and use 3rd party apps, you will be able to calibrate your printer quite nicely, and be able to bump up your print speeds and fine tune your print quality quite nicely.

I set the speed to low and it is still insanely fast (seems the same to me).  There are some smaller parts I'd like to print with a better chance of it not "missing" and overprinting.  How fast is "slow" supposed to be?

While I have it set to print pretty slow, I get much nicer prints from Cura than I can from XYZwares version of Slic3r. Any of the third party slicers will give you access to many "extra" settings that can improve your prints in some fashion.

While Cura's supports are not any more impressive than XYZwares, there are many other settings possible that do matter.
Brim is very useful, ability to directly set wall thickness as well as top and bottom of prints, setting first layer height and temps, and a lot of other somewhat lesser tweaks.

Some features that it has are truly cool, but not functional for the DaVinci. The biggest is probably it's ability to print a full bed of items one at a time, but with the belt being so close to the bed on the DaVinci, it really isn't worth setting up for most people. Last but not least is the fact that it will slice things that XYZware chokes on and never completes.