T-Mobile said it lost 93,000 subscribers in the second quarter but the Android platform and an expanded 3G network are giving it some positive news with long-term subscribers.

The fourth-largest U.S. carrier finished with 33.6 million total subscribers and a net income of $404 million. This places T-Mobile behind Sprint’s nearly 50 million subscribers and AT&T and Verizon Wireless are well ahead with almost three times the amount of users.

The T-Mobile loss of subscribers comes as the battle for the prepaid market is heating up. T-Mobile lost 199,000 net prepaid customers in the quarter – compared to a gain of 268.000 for the same quarter last year – as MetroPCS continues to gain steam and as Sprint’s prepaid division (Boost Mobile, Virgin Mobile, etc.) gets stronger.

While no carrier likes to lose customers, the average revenue per user isn’t that high on prepaid users and these customers are more likely to leave because there’s no long-term contract holding them. Because of this, it is a positive sign that T-Mobile added a net 106,000 subscribers on long-term contracts and the Android platform helped with this.

The carrier’s top-shelf smartphones are all Android devices and the myTouch 3G Slide and the Samsung Vibrant allowed it to boast about having 6.5 million smartphone users.

“In the second quarter of 2010, customers embraced T-Mobile USA’s industry leading value which makes it simple and affordable for consumers to trade-up to next generation products and services,” said Robert Dotson, President and CEO, T-Mobile, in a prepared statement. “The number of 3G smartphones in the hands of our customers year-over-year has tripled to 6.5 million supported by a network that offers the broadest reach of 4G speeds in the U.S. as our growth continues through data revenues.”

The company is also making a big push with its 3G network, which now covers 208 million people. It plans to upgrade the majority of the network to the super-fast HSPA+, which now covers 85 million people.

[Read the full results here]