You can read the complete Article #7 and Analysis here:
Switch vs 3DS and Wii U – VGChartz Gap Charts – October 2019
Switch Vs. 3DS and Wii U Global:
Gap change in latest month: 497,401 – 3DS and Wii U
Gap change over last 12 months: 2,040,880 – Switch
Total Lead: 3,177,933 – 3DS and Wii U
Switch Total Sales: 40,736,064
Switch was actually performing its worst exactly 12 months ago (comparison wise) which was month 20. Then it gained a lot of ground during months 21 and 22. Now go back 24 months to month 8. Switch lost ground 2 years ago going into the holidays (months 9 and 10).
This is because the 3DS was extremely front loaded. It got a huge price cut in less than a year's time. So while 3DS + Wii U seems like it's doing better against Switch, it's only because, combined, they shot ahead quickly. Switch gained ground 12 months ago and it's total should even shoot ahead of 3DS + Wii U after this holiday season.
In reality Switch has a very different sales curve than 3DS + Wii U, and that is because it is appealing to a much wider audience. Switch sales are still accelerating, while 3DS + Wii U is decelerating during the corresponding point in time. 12 months from now that Gap Chart is going to look extremely different and this time in Switch's favor.