I did a quick Google search and came up with this good link. Even though it's a SUSE site, the FAQ still applies for the most part. I thought this Q/A was especially pertinent to your question:

I'm unsure whether I should upgrade to apache2 or stick to apache1.

Apache 2 itself is stable, but it is missing (at the time of this writing) (Feb 13 2006 -ed.) some modules that are in common use (most notably, mod_perl and mod_php4). Those apache 2 modules are under development and it seems like a question of time when they appear. apache 1 and apache 2 can be installed on the same system. This facilitates evalation of the new version and allows for performance comparisons. The two versions can even be run in parallel. However, there is only one port 80 on your system. If you really need both versions of apache on one system, run one of them on another port and use mod_proxy with the port 80 server to map it into the URL space. Reasons to upgrade:

• • You want Ipv6 support
  • You want to run a Subversion server so need the mod_dav_svn module

Reasons not to upgrade:

• • You need an apache module that is not yet available or not stable (e.g., mod_perl or mod_php4) and you cannot take the risk to try out new software
  • You need another certain module that is only available for Apache 1

Apache 2, if built from the sources available from the apache site with the usual 'configure; make; make install' sequence, installs everything cleanly below one directory. Even the logs will be inside the server root. This is a very safe way of trying out Apache 2 without breaking anything on a running system which is maintained with RPM.