rghdc said..
When you gain enough experience in the water, riding a heavy board feels like you riding with seaweed wrapped around your fins after coming off a light weight board of similar design.
I would disagree with the comparison. An heavier board has more inertia, so it is slower to move, but once moving it keeps moving.
For instance on take off, with a 6kg board, you can just take off in one paddle stroke, with a 9kg board of the same length, you will need to accelerate through two paddle strokes. But a bit of chop can prevent your 6kg board to take off on the wave, unless you are adopting the proper stance (well bent forward fence) and focus to continuously drive the board through chop by your body weight.
Heavy boards have their advantages, depending on the goal. Although lighter boards are mandatory for the surfing demanded in current contests, heavier boards can be more fun for free surfing when you want to work your style, survive chop, or are not in the mood to be agressive. I have for instance a 8.8kg 8'3" for choppy conditions and relaxed moods and a 5.9kg 7'11" for aggressive moves. Getting a more expensive lighter 8'3" would not have made sense. Save your money for the boards you plan to ride aggressively.