I prefer this guy, the Do20K.
Same design (perch/splashguard), better mouthpiece (for me). I have the D020-w-2 and can't seem to adjust to the angle of the sidecar mouthpiece. I like to vape at a desk, and the sidecar makes me lean and twist my neck too much. If I hold it instead, then I have to concentrate on keeping it steady, as the perch is not as forgiving as a D020W (tire perch).
I like the GB-189 style sidecar.. the mouthpiece is angled more steeply to the vertical, so it can rest on my desk and is also comfortable to use.
Regardless, the new yingmang one and the sss ones would be required purchases if you own more than 4 or 5 of the China pieces. I'd put these guys just slightly behind my GB-187.
Also, whoever recommended putting oil on the GonG to Glass connection, thank you.. it works awesomely.
Edited to add:
@blankrider - how's that carbed GonG working out? I'm tempted to get one.