UPDATE 2-MetroPCS Q1 customer additions beat estimates

(Recasts; adds details, comments from analyst notes, share movement)

April 7 (Reuters) - Low-cost mobile phone service provider MetroPCS Communications Inc (PCS.N: Quote, Profile, Research, Stock Buzz) posted better-than-expected net customer additions in the first quarter due to robust growth in both new and old markets.

The company was particularly helped by faster growth in the Los Angeles market, which it entered in the third quarter, and benefited from ongoing landline replacements in the United States. MetroPCS has also been arguing that it stands to gain from the U.S. economic downturn as customers pull back on their spending and look for cheaper options.

Its stock rose as much as 7.6 percent and was trading up 2.2 percent at $19 in morning trade on the New York Stock Exchange. Shares of rival Leap Wireless International Inc (LEAP.O: Quote, Profile, Research, Stock Buzz) were up 5 percent at $54 on the Nasdaq.

The results showed the continued growth potential of MetroPCS's legacy markets and demonstrated that the Los Angeles market was meeting expectations, Bear Stearns analyst Phil Cusick said in a research note.

In the first quarter, MetroPCS added about 315,000 net subscribers in newer markets, including Los Angeles, an increase of about 16 percent.

The company said it posted first-quarter net subscriber additions of about 452,000, a marginal fall from the previous year when it benefited from more entries into new markets. Churn, a measure of customer attrition, was unchanged at 4 percent.

Bear Stearns' Cusick and and Stanford Group's Michael Nelson were expecting net additions of 405,000 and 410,000, respectively. They expected a churn rate of 4.4 percent.

MetroPCS and Leap typically target youth and ethnic minorities with relatively lower earnings power by offering unlimited calls at flat monthly rates without tying customers to contracts.