The built-in iTunes visualizer is actually based on G-Force, not Whitecap. And I agreee, G-Force is about the best out there! More options and variety, but basically similar to the built-in one.
On the other hand, I've noticed Apple's version running faster at the same 640 res--and most importantly, I do like the album art which Apple displays.
Why aren't there more (any?) album art visualizers? I'd like to see the art big! iTunes does store the art larger than a thumbnail--click and you can see it full size (whatever size was imported).