Enlarge (credit: Verizon)

Verizon Wireless is once again selling an unlimited smartphone data plan. Verizon had stopped offering unlimited data to new customers in 2011 but has been facing pressure from T-Mobile USA’s new unlimited offering.

Verizon initially responded to the competition by pointing out that (unlike T-Mobile) it doesn’t impose limits on video quality and arguing that customers are better off using the nation’s best network even if they don’t have an unlimited data plan. But today, Verizon has started selling an unlimited plan that costs $80 a month for a single smartphone, $140 for two lines, $162 for three lines, and $180 for four lines. (These prices include the monthly “line access” charges, but not taxes and other fees.)

While T-Mobile’s $70 unlimited plan limits streaming video quality to 480p, Verizon told Ars that “We deliver whatever the content provider gives us. We don’t manipulate the data.” In practice, 480p looks pretty good on a smartphone screen, but it’s an advantage for Verizon among customers who don’t want any video quality limitations.