Apache is Apache, but builds can be different, depending on the system they were compiled for (eg Intel or PPC), the version of Apache, where it will reside on the server, and the optional modules you choose to add in when you build it (eg SSL, Proxy, PHP). There seems to be a dearth of decent Mac builds for Apache 2 at the moment, particularly for the Intel Macs.
Ive had no problem with PHP5, but some have - the entropy build of PHP5 for example, which is very nice, was initially done for Apache 1.3 (the one that comes with OSX) and so wouldn't work properly with Apache 2. I believe he has a newer build out that supports it now.
From memory Apache 2.0.5.9 builds a module for PHP4 by default, so if you want to use PHP5 you have to have a build that supplies the libphp5.so module for Apache to use to access it (and comment out the php4 library in the conf file)
The MAMP build lets you choose PHP4 or 5 to use, and it works well, but it's a development platform, not something you'd use in a production environment.