[GENERAL] is it good to disable autovacuum and schedule routine vacuum process?

[AI Rumman]

I am using Postgresql 9.0.1.
I want to know which one is good regarding  VACUUM - Routine VACUUM manualy
or AutoVacuum.
Recently, I found in my production that  some tables were not vacuumed for a
good period of time when the autovacuum was enabled and the DB was slow. I
vacuumed the DB manually and the performance was good.
Can anyone explain why this was happened and is it good to disable
autovacuum and schedule routine vacuum process?