That article had something I've never seen before: the concept of "express download" size in WU. For example: KB2919355: 690.0MB vs 112.2MB That'll make a huge difference (considering hundreds of millions of clients) if the largest piece of the update is reduced that much in WU. I assume this is done by WU determining which components the user already has (from prior updates), as opposed to the MSU, which assumes that the user has none?
Does this KB2949621-v2 update fix some memory leaks or something related to performance? After installing the update and without reboot, my pc is faster? Hmm...I mean there is a difference in the performance!