I'll be using my server for a starting web hosting company. I'm wondering if it's better to use PHPSuexec and Suexec from the beginning (or not to use it at all!).
SuExec is an absolute must no matter what!
Now with that out of the way, let's talk about PHP ...
Personally, I do not recommend phpSuExec because it cause more security problems
than it solves and it's advantages are limited because you can track usage of scripts
with more advanced logging (easy to setup) and don't really need PHP scripts to
be executed as the user ID if your concern is tracking script usage.
If your concern is that of users on the same server accessing each others files then
that is an area where you might consider phpSuExec but I would still lean away from it
for both performance and security reasons.
Now, if your are using Apache 2.x or 2.2.x then I will take the exact opposite argument
and recommend you go with SuPHP which provides the same functionality as phpSuExec
but doesn't have any of the additional security problems that phpSuExec brings!