Nginx support

[apinto]

varnish don't support ssl nginx yes and it can replace apache.

Varnish might not support SSL, but that is not the point here.
Varnish Cache does not support SSL, however Varnish Reverse Proxy and Load Balancer supports SSL.
(however you can still support SSL http://davidbu.ch/mann/blog/2015-03-20/v...pache.html but I believe it is not the best pick).

NGinx will create a entry barrier, most users have familiarity with apache and .htaccess files and there are plenty of newbiew resources on the internet available for apache.
Using NGinx only for speed will change Sentora userbase (I'm not even saying we will have less users, only different users).
Not even speaking about the upgrade considerations and the support needed to accommodate that.
I do not believe NGinx is a viable alternative at this moment for Sentora for various reasons already stated above.

For speed and load balancing Varnish is a easy drop-in alternative that brings nothing negative, the user will keep using apache (just on a different port).