For what it is worth...
After every update to Logic, (or in many cases a major upgrade to OS X) there seems to be a small group of people for whom the update causes a perceived or real drop in performance...
It's often hard to properly identify why this occurs as it certainly doesn't affect everyone....
Some examples of the most common causes have been found to be;
1) The particular hardware they are using.... Certain Graphic cards.... Audio interfaces... even certain external Hard Drives etc.... and the use of USB2/3 ports...
2) 3rd party plugins.... other related drivers.. Other software installed on the same Mac... Conflicts with such software... older unused drivers lurking around..
3) Bad habits in the use of Logic ( that didn't really affect performance in earlier or in some cases later versions..until things changed) like leaving Analyze mode on in EQ once you have completed EQ'ing or using multiple copies of a CPU hungry plugin when you could bus it... and use just one copy.
4) Changes in libraries or other such routines in OS X or that Logic accesses...that do place greater demands on any given Mac's hardware... and if you happen to have certain types of hardware you will notice the drop more than others...
Methods of working in / The general work flows used with Logic can explain the differences some people see in terms of performance... Example, some people use a given built in plugin such as an EQ or Compressor, more than others might and so that do, and if thats the plugin that now needs more CPU resources.. those people will notice a greater drop in performance... compared to people that dont use those plugins to the same degree.
I have three El Cap and LPX testbed 2014/2015 iMac rigs here and on all three, the combo of 10.2.1 and OS X 10.11.2, 10.11.3 and 10.11.4 seems to provide for either a very small boost in performance or pretty much the same as it was before in 10.2. Certainly no noticeable drop in performance across multiple projects created originally in 10.2
Does that mean, there is no real problem? No.. but again, its just an example of how different setups may be affected by certain changes, than others... and not always negatively.
I know this post isn't that helpful to those seeing such an issue but I thought it was worth mentioning never the less... and for those that do, make sure you are using the latest versions of whatever other software/drivers and plugins you may have installed... that are also compatible with the version of OS X you are running under. One errant plugin or driver for example, can trip up a system...... causing poor performance..
I'd also recommend loading up such a project where you have an overload issue and run Etrecheck...
http://www.etrecheck.com
Look carefully through the report and see if anything stands out that could be the root cause of your issues.. like unused or out of date drivers/ apps.. Stuff running in the Foreground /Background that you dont use...or need..... Any Adware present and so on.... Sometimes doing this will improve if not fully resolve such problems..
Finally, of course... you dont always need to have the latest and greatest software installed..... Sometimes it's better to stick with a combination of Logic and OS X that works best for your setup... This is why several of us here still run a combo of 10.6.8 and Logic Pro 9.1.6 or 8. That particular combo is stable as heck and runs like a dream. Sure, we cant use the latest plugins.. and yes, we are probably missing out on some new Logic features.. and yes, we have to maintain our old hardware in order to be able to do this... but at the end of the day its all about making music in a relaxed yet efficient way..... and a stable setup you understand inside and out, often provides for that.
Just some thoughts i wanted to share... and as always, each to their own 🙂
Cheers..
Nigel
