Unless you recompile mod_php and all its extensions to be thread-safety, the most manegeable and performant solution will always be:
Apache w/ mpm_event + mox_proxy_fcgi -> php-fpm
Besides php-fpm is a very complete daemon/service to serve php, it allows for different pools with pretty different configurations/users/permissions/paths, etc. and to have a separate service for php content helps much.
For example, an added benefit from this setup is, for the not too experienced, it helps to determine when the issue is php and when the issue is Apache.
I see lots of folks in stackoverflow or asking for help in the #httpd channel at Freenode who confuse their problems as Apache being the source of them instead of PHP scripts or the php configuration itself.
