Following stats from comScore late last month for smartphone market share by vendor and OS, research firm Kantar Worldpanel is out today with its own numbers for the three month period ending in May. While Kantar puts Android at the same 52% of the market during May as comScore, it has Apple slightly higher at 41.9% of the market (up 3.5% from the same period last year) compared to the 39% comScore reported:

Kantar notes that Apple’s increase is thanks to T-Mobile picking up the iPhone 5, which is now the best selling smartphone at the carrier despite only being available since mid April. Thanks to iPhone, T-Mobile could soon increase its share of smartphone sales in the US, as Kantar notes all iPhone models counted for 31% of the carrier’s smartphone sales during the quarter. Currently the carrier holds just 10.1% behind Verizon (34.6%), AT&T (29%), and Sprint (12.7%).

The report notes T-Mobile has been attracting a lot of first time smartphone buyers since getting the iPhone with around 53% upgrading from feature phones:

“iOS’ strength on T-Mobile appears to be the ability to attract first time smartphone buyers, upgrading from a featurephone. Of T-Mobile consumers who bought an iOS device since it launched on the carrier, 53% had previously owned a featurephone, well above the market average of 45% of iOS owners who previously owned a featurephone.”

“Furthermore, of T-Mobile customers planning to change device within the coming year, 28% plan to upgrade to an iPhone for their next device

As for Windows Phone, Kantar has 4.6%, up 0.9% since last year, while late last month comScore had it at 3.0% just under BlackBerry at 4.8%. Kantar doesn’t provide numbers for BlackBerry but notes that its data “tracks mobile phone behavior and the customer journey, including purchasing of phones, mobile phone bills/airtime, and source of purchase and phone usage.”