Composite poles CAN be lighter than aluminum poles. The term composite is quite vague and can include fiberglass, carbon, graphite, and kevlar. The cheaper the cost, the higher the fiberglass content. The more expensive, the higher the graphite content.
Shapes vary and therefore flex will as well. Constant thin diameter poles such as Goode offer a flexy shaft for better shock absorbsion, tapered shafts from thin at the basket to thick at the grip are generally stiffer.
The lowest price point composite poles are fibreglass with a dark resin to emulate graphite. These poles are generally heavier than a similar priced aluminum pole. As more carbon and graphite are added to the mixture, the price goes up, and the weight goes down.
I prefer a light high quality aluminum pole, since they are much cheaper, and can weigh as little as some of the lighter composite poles. If I damage or lose an aluminum pole, it doesn't hurt the wallet as much. Very cheap aluminum poles are very soft, and can bend just by thinking about it. As price goes up with alu poles, so does the strength. Like composite, instead of bending, they break when stressed to much. That said, a better alu pole will flex more than a cheap one, and return to straight once a the stress has been let off.
You will get what you pay for. Spend more, get more, and cry more when they break or get stolen.