Should you ditch Apache?
In my experience (using Nginx + PHP for about 3.5 years) it's a wonderful choice and I would never go back to Apache. There are two main advantages:
Reduced memory usage: Using Apache, PHP is loaded inside the webserver itself. If you have 80 Apache processes listening, everyone of them will run a different PHP environment, using 20-30MB of RAM each. Nginx, on the other hand, communicates with a bunch of php-fpm
processes which you can scale separately. I usually have to run only 3-4 PHP processes, so this drastically reduces my memory usage.
Very fast static assets: Nginx is faster than Apache at serving static assets (CSS, JS, images, ...), and uses very little memory to do so.
One possible drawback is the lack of .htaccess
files support. This means that if the PHP software you're using relies on this type of file and doesn't directly offer Nginx configuration examples, you will have to "translate" the Apache .htaccess
file to a format that Nginx understands. In my experience, I had to do it for a couple of Wordpress plugins. Again, it's not too complicated and you can usually find someone who has already done it by googling.
The other thing to keep in mind is that Nginx+PHP-FPM is not some kind of magical panacea. If you have crappy, slow PHP code, this won't fix it. I have limited experience with Magento so I cannot offer you any specific insight. In the case of Wordpress (which I consider extremely bloated), Nginx is indeed a lot faster at serving static content, uses less memory and is a bit faster at serving PHP pages, but it certainly doesn't cut your PHP execution time in half ;)
Nginx vs Lighttpd
Nginx has recently gained a lot of popularity. Its usage has almost doubled in the last year and it's already 16 times more used than Lighttpd based on these statistics.
There doesn't seem to be a huge difference in performance between the two, so I would definitely go with Nginx.
Keep in mind that you will have to use PHP as php-fpm
. It's not that difficult to configure, and there are countless, easy tutorials on how to make them work together.
Edit: Sorry I re-organized my answer, I kind of missed the point of your question at first.