May 2018 is the 15th month that the Nintendo Switch has been available for. During the latest month the gap grew in favor of the Switch by 172,041 units when compared to the 3DS during the same timeframe and by 184,097 units in the last 12 months. The Switch is currently ahead of the 3DS by 1.10 million units.
The 3DS launched in February 2011 (however, 3DS sales have been aligned to March 2011, since it only launched at the end of February in Japan), while the Nintendo Switch launched worldwide in March 2017. The Switch has sold 17.33 million units, while the 3DS sold 16.23 million units during the same timeframe.