Some companies have created ways to lighten the weight of the truck, while keeping the durability. Grind Kings and Thunders are on the lighter side, while Independent and Destroyer are heavier. Keep in mind that almost all trucks fall between 10 and 13 ounces. If you really think that taking six ounces off your board will make you skate better, go for it. But maybe you should close your eyes and see if you can tell the difference.
Most trucks are available in a few different widths, as well.
Well, if it's too big, you'll look like a turtle, and if its too small, you won't be able to see them while riding. Your truck bolts should be flush with your board, so it depends on what size board you ride. In the past few years, there have been many different variations on trucks, to provide a bit of diversity to your board. For example, Tensor Trucks offer a plastic piece in the base plate, to assist with tricks like nose slides and tail slides. Some companies offer a non-slip axle guarantee.