As an example, I would refer you to a discussion down this thread about Apache 1.x forking for concurrent connections.
It's nowhere near that simple. You can fork lightweight like threads or heavy. One of the terrible things about Apache performance was all the heavy forking on every single request for generated pages. That was back when it was really expensive.
Nginx requires an openssl version that supports sni -- that was added in 0.9.8f on Oct 2007 (if you compiled openssl manually to enable it), and was enabled by default in 0.9.8j on Jan 2009.
Apache supported SNI using mod_gnutls since 2005; and in 2.2.12 (July 2009) using openssl.
They should never be used unless you're in a shared hosting environment where you don't have a choice.
Debian e.g. only received 2.4 with Jessie. Meanwhile, a feature-comparable nginx was available at least in Wheezy, maybe earlier.
If I have to choose between "compile my own Apache" and "just install nginx", well… Actually, I had to choose, and I picked nginx.
FTA: In February 2012, the Apache 2.4.x branch was released to the public. Although this latest release of Apache has added new multi-processing core modules and new proxy modules aimed at enhancing scalability and performance, it's too soon to tell if its performance, concurrency and resource utilization are now on par with, or better than, pure event-driven web servers. It would be very nice to see Apache application servers scale better with the new version, though, as it could potentially alleviate bottlenecks on the backend side which still often remain unsolved in typical nginx-plus-Apache web configurations.
I'm using Apache 2.4 with mpm_event + mod_proxy_fcgid and it's doing fine - 99% of the work and time spend is done in the FastCGI application anyway and for static content mpm_event is good enough. I wouldn't run a dedicated static CDN box on Apache but for everything that can run on a single server Apache can also do the job... even HTTP/2 with mod_h2 works fine as of 2.4.17
A problem with nginx is to figure out what matches in a complex config... it's not straightforward. .htaccess is nice and simple for a shared server with lot's of users.
I really like nginx but I guess most people just don't really need it. Migrating to 2.4 and mpm_event should be good enough.