Railing first and foremost is for safety. Make sure to check your local building code for regulations before construction. In the area that I work in, railings must rise a minimum 36 inches from the surface of your deck if below 6 feet, and 48 inches if your deck is above 6 feet. No space between the surface or pickets can be greater than 4 inches. The railing has to be non-climbable (no horizontal rail or benches without 36/48 inch backs). The last is the most loosely defined as easily graspable. Easily graspable to me means a smooth finish for wood or aluminum; Regal aluminum railing can be too thick for some but they just released a slimmer design.
For every type of composite, there is another type of aluminum. I can install any of them, but Regal seems to be the most common. I have never had a warranty issue on any aluminum rail, and it goes in perfect every time. I highly recommend investing in a aluminum rail system. Each manufacturer typically has black, white, and 2 other colors. With different combinations of glass and pickets. The 2 big mistakes home owners make when doing an aluminum rail are placing the post in the middle of a window view or not supporting glass properly. Make sure to read manufacturer instructions and plan ahead to avoid both mistakes.
The possibilities with wood are endless. Google has many different types of railing ideas, but make sure to pre-plan your railing before you start your deck project. The most important decision is whether you want to embed your posts into the frame or secure your posts to the outside of the frame. If choosing a decorative picket such as a colonial picket, be sure to choose an exterior coating with a strong UV inhibitor (oil, acrylic or latex)
Vinyl railings give the appearance of wooden style railings and pickets with the wind and weather resistance of a more eco-friendly choice. And no staining! Vinyl railing is more cost effective than aluminum, and can be cleaned with a white eraser.