One of the biggest differences between the two ISPs is availability. While CenturyLink is available in 36 states, Cox is available in only 18 states. Further, CenturyLink offers fiber networks in 50 states, while Cox offers fiber to their business customers only.
If you don’t have access to CenturyLink Fiber, Cox is your best option for internet service. Cox has more cable internet plans than CenturyLink’s offerings. However, you may want to consider CenturyLink for its gigabit internet plan; it’s cheaper than Cox’s gigabit plan. If you compare the lowest-priced plans from both providers, CenturyLink’s cheapest non-fiber plan is $50 per month, whereas Cox’s is $53 per month.