It comes down to priorities.
The Cane Creek 40 Series ZeroStack headset is modeled after Cane Creek’s 110-series headset. The most noticeable difference is the finish. Where the 110 is a gloss black, the 40 opts for a satin look. There are a couple of internal differences, as well. Whether they are worth the difference in price is the question.
Looks aside, the 40-Series Headset is crafted from 6061 T6 alloy where the 110 headset has cups machined from 7075 T6 aluminum. The functional difference is one of a few grams, with the higher tech alloy of the 110 headset allowing a lighter overall part. This 40-Series Headset spins on Cane Creek's black oxide bearings. The races and balls start out as 52100 steel and are then given an acid bath to make them more corrosion resistant, while still being porous enough to retain grease. They are angular contact bearings (ACB), which resist both axial and radial loads equally well. The cartridges are sealed with what Cane Creek likes to call a Split Lip Seal, which has two contact seals per side to better keep out contaminants and hold in grease.
To augment the seals on the cartridge bearings, Cane Creek adds face seals to the crown race and top assembly. So what if the bearings aren't stainless like the 110 Headset — grease kept in and muddy goop kept out keeps 'em running like new for a long time. In the event that you might wreck the bearings through normal use or abuse, you should know that all the internal parts in this 40-Series Headset are compatible with their top-of-the-line 110-Series Headset. So you could always upgrade to the 110 headset's stainless steel bearings. The Clip-Seal in the upper assembly holds all the parts together, including the compression ring. This makes assembly a cinch, since there are no loose parts to misplace or install backward.