Installation with sources or with packages

Hello,

I need install postgresql 8.X.X on my debian host.
But someone says me I should use sources files for the install
and other one says me I should use debian package.
Does anybody have some "theory" or opinion about the installation of postgresql
by sources or debian package ?

What's the most reliable/best solution to install AND UPDATE the sgbdr during
his all life ?

thanks for your help.