Originally Posted by Jipe

No, the 12s has a Surmey-Archer 3s hub almost identical as the one of the 6s, the only difference is that it accepts 4 cogs instead of 2.

Combined with this hub, there is a new "advanced" derailleur with 4s instead of 2s which is more reliable/less sensitive to dirt than the 2 s derailleur.

So the advantage of the 12s vs. the 6s is a bigger gear inch range, smaller gaps between the gears and a more reliable derailleur.

For new bikes, the price difference between the 6s and 12s is very small with as consequence that a used 6s should become cheaper than it was before the 12s.