Using custom blog or prebuilt blog with existing PHP site (such as one built on

A developer spent over a month integrating WordPress MU with an

existing php site. Basically, the task was to ensure that when the

user logs into main site, they are already logged into blog. In other

words, they don't need to log in twice. Also the admin should be the

admin of main site, so the admin of main site has privilege to edit

posts by users. There were a number of issues encountered while trying

to integrate WordPress MU including database structure.

Ultimately, I felt that all the time spent on this project, it would

have been better time spent using a php framework like codeigniter and

building the blog from scratch using this framework. It would have

probably taking equal amount of time and been more robust.

This blog would be important to site but it won't be the site (the

site would have a lot of other custom PHP functionality developed from

scratch), expecting thousands of visitors and therefore performance

must be strong and bugs must be minimal.

In the future, should I use a prebuilt blog tool such as WordPress MU

or should I build blog from scratch on top of an mvc framework like

codeignitor?

The site has already been developed in PHP and future versions will be

developed using codeigniter, so I will never build the whole thing on

top of something like wordpress. I am just referring to the blog

component, whether I should use existing blog software such as

WordPress MU (or is there something better?) or build it from scratch

and why should I choose one over the other.

Thanks for response.