I think both styles look wonderful!.. I prefer the light version... but I'm just not too fond of dark ones..LOL
I did have one minor suggestion.. This graphic..

.. I would recommend taking the word old off of it.. The *new* graphic is great.. but just having the word old implies that the forum is not popular and therefore does not have anything new in it.. It is a negative thought about your forums.. I think if it was just a plain and then had the *new* graphic when something is new.. would be better.. IMO..
Other than that.. Great job!!!