Most importantly the cost and available choices of materials. I mostly order athttps://www.123-3d.nl/ as they offer a lot of choice and deliver relatively fast. They are also pretty close meaning if something goes wrong it’s easy to interact with them.
There house brand is pretty decent and reliable in my experience.
Heretic! Get to making more things before we throw you out. 
I had issues with the Snapmaker filament early on. Switched to Hatchbox and have never had an issue; regardless of color or material. You get one chance to win or loose my business and Snapmaker lost out of the gate.
I actually DO buy filament from Snapmaker, but I would like some better choices on color. You have some other choices in PET, but I, at this point, only print in PLA. So some more variants there would be great, like primary and secondary colors, as well as earth tones especially a leaf green. Also, since you sell PET, have you considered selling a completely recycled line of PET. Like MTN Dew green? That would coax me into trying PET.
3DJake delivers fast.
Need good quality ABS.
Fiberlogy ABS black, 1,75 mm / 850 g
Tuotenro.: FL-ABS-BLACK-175-085
24,49 €
that gave me my smile for the day