This powered armor appears to be composed of entirely of lightweight ceramic composites rather than the usual combination of metal and ceramic plates. It seems as though it should give even more protection than the standard advanced power armor.
The advanced power armor Mk II is a model of power armor used exclusively by the Enclave military forces, developed after the Great War. Like its older brother, the standard advanced power armor, it's matte black with a menacing appearance, but with a few significant differences - it appears to be composed entirely of lightweight ceramic composites rather than the usual combination of metal and ceramic plates.
Advanced power armor Mk II is apparently present in Fallout 3 known as Enclave power armor. However, those versions almost entirely different, bearing a stronger resemblance to power armor from Fallout Tactics: Brotherhood of Steel than to the originals, despite being referred to as "advanced power armor Mk II" by Brotherhood and other non-player characters including the Brotherhood Outcast leader, Protector Henry Casdin.
A possible explanation for the discrepancy cited above could be that the suits used by Enclave soldiers in the Capital Wasteland are simply different incarnations of the same model. Timeline references indicated that the Enclave had created numerous power armor prototypes and concepts in their attempts to improve on the "gold standard" set by T-51b power armor, many of which were less effective than the T-51b. Just as Eastern Brotherhood of Steel soldiers had to rely on the older, inferior T-45d power armor to equip their forces due to the majority of T-51b suits being assigned to the Core Region chapters, perhaps Enclave cells on the east coast were similarly underprioritized. However in Fallout: New Vegas there exists in the game code the Fallout 3 Enclave power armor under the name Enclave Shock Trooper armor. It could be theorized that this is advanced power armor Mk II but a sub variant that is not designated differently.