Open Lite Speed hands down beat the hell out of nginx + apache in the way they are setup in Plesk.
Same identical server that hold 200 domains on Plesk (most of them on NGINX) were hitting 50% of the CPU on a Ryzen 5 5600.
Same identical server with those 200 domains on Webuzo with Open Lite Speed and I get less than 20% of CPU usage.
This is because Plesk made it so difficult to use native nginx, even when you have EVERYTHING setup properly, there will be sites that ends up using the proxy. So you are never 100% in control of what happens.
I already tried going domain by domain and pushing an NGINX only setup. Also tried making sure that the subscriptions attached to the user were not using any proxy, but Plesk insist on enabling the proxy from time to time and I completely lost any hope they are going to fix it.
With Open Lite Speed it's just Open Lite Speed, there is no margin of error to call upon Apache or any other webserver and the way it handles the LSPHP processes is way more efficient. I won't go into details. Suffice to say, at the end of the day, those same servers are more efficient and allows my customers to run more snappy installations due to less overhead on the background.
I am sorry, but this is comparing apples with pears.
And that is exactly the promise of Open Lite Speed, as demonstrated on their own page : a comparison of "speed" (i.e. performance) of WordPress sites on Open Lite Speed (LSCache) with Nginx (FastCGI cache) and Apache (W3 Total Cache).
I am not sure whether you compare 200 domains with WP instances or not.
However, the comparison of various alternatives with (very) specific caching mechanisms is very lopsided by nature.
Each and every caching mechanism is designed to serve a specific purpose.
Nginx is to some high degree different, in the sense that it is provided with a huge amount of "building blocks", allowing to serve multiple caching purposes.
Nevertheless, Nginx is born as a reverse proxy server, not as a caching mechanism.
So yes, there is the huge difference to start with.
In addition, when combining "building blocks" with Nginx, one still serves one or a couple of purposes - for instance, allowing caching modules with Nginx will result in a reverse proxy server with caching functionality.
Again, the primary objective is the reverse proxy server and the secondary objective is caching on the proxy server level.
This is primary + secondary objective combined is more or less the same to Open Lite Speed, with this difference that Nginx - the reverse proxy server itself - is more controllable and that the Nginx modular system is more flexible and can be augmented with each and every module one likes to add.
In essence, Open Lite Speed serves a specific purpose and is limited to that purpose - it is as good as it is programmed.
To be fair, Nginx might be less limited and the Nginx core might be excellently coded and the Nginx system might be more flexible, it still is limited.
In fact, Nginx is limited by the extent to which the implementation has been done properly.
More importantly, Nginx is often limited by the fact that the vast combinations in the setup of core and modules can create a performance pitfall - for most people, it is not clear how and when specific combinations will result in issues.
This is exactly the problem with Plesk.
Plesk has been configured in such a way that the default Nginx setup can never be optimal when activating Nginx based caching.
Stated differently, this well-known problem has been present for years and cannot be solved by tweaking settings in Plesk Panel or by adding custom Nginx config files on the server - one really has to create custom Nginx templates (and thanks to the nature of Plesk, the presence of these custom templates will always create issues of both minor and major degree).
So yes, one can conclude that Plesk with Nginx based caching will be outperformed frequently (but not always) by other caching solutions.
However, it still is a comparison of apples and pears.
Any pure Nginx configuration - without the burden of Plesk based default Nginx config - will always outperform all other caching solutions.
The problem is only that one needs to define "outperformance" - speed? resource usage? memory usage? request performance?
A proper and neutral definition of "outperformance" cannot be provided, in my humble opinion.
After all, optimal caching solutions should be dynamical - each every solution can only be optimal when being optimized for that one specific purpose that is the objective, with optimization being a dynamical process (and not static).
No site is the same and even situations to be optimized will change each and every second for individual sites.
Having a Ferrari, Porche or Lamborghini that can go fast does not imply that one will drive fast continuously, right?
Having an optimal caching solution that is "good on average" is often the best one can do.
Sure, Nginx can be programmed to dynamically adjust to each and every situation ...... in theory and practice ....... but should I care about each and every situation that can or might occur and that requires a (small or big) tweak in caching settings?
No.
If Open Lite Speed works for you, then that is good.
If Plesk with Nginx based caching does not work for you ......... well, that is predictable - this is an issue for almost every Plesk Panel owner.
I sincerely hope that Plesk Team will have a look at this Nginx related challenge soon - fingers crossed.
Kind regards......