Literally everybody has the qualifier switch when they said that its a great month.
Only person who does not is somebody who asked if this is a impressive month, coupling that with asking for last years numbers.
Comparision is quite easy since both 3DS and Switch released in march, but take it with a grain of salt anyway.
2 FY after launch, 3DS sold 31M worldwide, and 10.2 in the "americas" region which includes USA where NPD reports on.
1.75m after launch Switch sold 32.2M worldwide, and 12.9M in the "americas region.
If we add in the 1M NPD told us and the 1M from Japan, Switch is ahead of 3DS by at least 4 million launch aligned Worldwide for the first 2FY, and at least 3.7M in the Americas region.
That is impressive in several ways, be it that Switch is outpacing 3DS which ended up selling over 80M worldwide, or that it is doing so at a much higher pricepoint, with so far no revisions or significant pricecuts.