Charging cables have an effect on how quickly a phone charges but is not the only factor

This is where the magic happens and where the most improvement can be made. These adapters change the wall output (120VAC) into usable power, about 5–12 volts. These also limit the current going into your phone about 1.25–3A (as to not make your phone explode). The cable going into this adapter can handle a lot more current than you will ever put through it. (NOTE: there are some very cheap cables that will overheat because of poor insulation and design but lets keep this to the theory) So after the cable the power enters your phone it is stored in your battery. Here the phone makes a important decision, it can communicate with the wall adapter and decide if it wants to receive more current to charge faster. This depends on heat and the charging capabilities of the phone. So to answer your question the cable is a factor but isn't the sole reason your phone might be charging slowly. A good charging experience starts with the wall adapter a cable designed to work with your device (length is a very small factor of charging).