Apple just released the second beta for OS X 10.11.5 El Capitan developers. For now, what we know of this second beta of OS X 10.11.5 is more or less what we have seen in previous versions, an overall performance improvement and typical bug fixes about the previous version of the operating system.
This new version of OS X 10.11.5 that comes with build 15F24b, it is an improvement of the first beta for developers and does not seem to have major changes. All this is very recent and it is necessary for the developers to do some research on the lines of code in this new version and see if it is really only about adjustments in the performance of the system.
The improvements in this version or the points where Apple wants to focus developers are Wi-Fi connectivity, Bluetooth and others. The beta of iOS 9.3.2 beta 2 is also in the hands of the developers for a while and it is sure that it improves some points of the previous beta version that had some bugs.
On the other hand, and how I always do not get tired of pointing out that when dealing with beta versions it is best to stay out of their installation and wait for an official version, but if you feel like trying and looking for yourself the news that is added in the new beta versions, it is best to wait for the public beta version to be released in the next few hours. To perform these installations I always advise using a partition on the main disk or using an external hard disk directly.