Search in front page vs search in forum

Neil Gaiman

   For searching around the forum we have 2 ways:
1. on the front page we have the Search box and you can select "forum" in the drop-down list.
2. the Search function in the forum itself.

My experience seems to tell me that the forum Search, although if it may look more powerful offering quite some filters, is rather crappy and will often return no results, while the front page Search will find something (whether it's what you were searching for or not is another story).

Test case: let's say i want to discuss what is the ideal lenght of a review. I'm pretty sure that this has been discussed before so before starting a new thread I search for already existing threads on the subject.

On the forum search I typed as Keywords "ideal lenght review", in the drop-down list I select "match all words", as options I select "all forums" and "find posts = any date".
The search returns no results.

Then i try on the front page search: I type exactly the same words "ideal lenght review", select "forum" in the drop-down list and press enter. Many entries are found. Many are about ideal album lenght or whatever, but scrolling a bit around I find a couple of threads discussing the ideal lenght of a review.

Why are the search engines in front page (selecting search in the forum) and the forum search itself so different?
It gives a poor image of inconsistency to the site.

What are yor tips for efficient searching around the forum?