This type of gear is known as a "herringbone" gear. A traditional straight-cut gear is strong, but can cause more vibration as each tooth engages and disengages. A helical gear (slanted tooth) reduces that vibration as the tooth engagement is more uniform. However the angle of the teeth causes a sideways force that may be undesired. A herringbone tooth design effectively cancels the sideways forces but gets the uniform tooth engagement.
A search for "herringbone" on Thingiverse comes up with many gears of this type.
Regarding the quality, if you are not happy with the results of your own design, that's OK - gears are shockingly complex, and people make careers of gear design! However, if you have a good CAD model that just isn't printing well, it's not likely a bad STL.
An STL from a different source is likely to have similar quality with the same slicer/printer setup. You might be able to improve print quality of your design by changing settings on your slicer or adjusting your printer. I'd suggest asking a question with your current setup and specific print quality issues.