With only 1500-2500 km per chain, the lubricant they are using is absolutely dismal.
Anyway, whenever friction is tested, Dura-ace 11 speed chains come out on or near the top, so that's what I use. Regarding the test the graph is derived from, I quote:
"This is explained by the Dura-Ace chain sample coming out of the box with a measured .12mm “wear” on the KMC digital chain checker, whereas the batch of Ultegra chains started at .05/.06mm measurable “wear”. Keep in mind that Kerin’s test considers .5mm to be worn out, and so .12mm is almost a quarter of the allowable wear allowance. Kerin believes this is a batch variance, and that it’s quite possible (even likely) the Dura-Ace chain can offer improved durability."