InnoDB & MyISAM

InnoDB supports foreign key, the cascaded on delete and update is very helpful, recommended for environment require strong data integrity and validity. But the trade-off is the data retrieval speed for SELECT statement.

MyISAM is good for deployment and fast in data retrieval, i think it is critical for forum usage which is mostly data read.

There is no best solution for all cases, that's why InnoDB and MyISAM co-exist, choose the one suits your needs. If your application is relying on data integrity and critical on read speed at the same time, try MySQL clustering, use InnoDB as master db for INSERT/UPDATE/DELETE, use MyISAM as slave db for SELECT, data updated in master will be trigger and propagate to slave db for synchronization.