You missing point, they are stronger, but with fact they are better without price cut and revision that 3DS had in that time period, conclude they are much healthier/stronger:
-3DS FY 2012. - 13.5m vs Switch FY 2017. - 15m (note 3DS had huge price cut only 6 months after launch)
-3DS FY 2013. - 14m vs Switch FY 2018. - around 17m (note: 3DS had revision)
-3DS FY 2014. - 12.2m vs Switch FY 2019. - expected somewhere around 20m (with all thing counting, like very strong lineup, price cut and revision)
Talking about games, 3DS also had strong games in its first two full FYs.
I agree that Switch will have similar pace to 3DS in sales than to Wii (and buy that I think sales want fail of a cliff like in case of Wii and longer life span like 3DS), with diffrence that Switch will have quite stronger sales per years, and we already have situation where Switch will sell 3m units more in its 2nd full FY than 3DS did, and in 3rd year difference will be even bigger (easily 7m+, because 3DS had 12.2m year in FY 2014), not to mentioned 4. FY where 3DS sold 8.7m.
But its not point what you think about, but point is about things we do know: just currently confirmed 2019. games: NSMBU DX, Yoshi, Pokemon Gen 8, Animal Crossing, Fire Emblem, Luigi's Mansion 3, Daemon X Machina, Marvel Ultimate Alliance 3, Town...in same period of last year what we know about 2018. lineup was only Kirby, Mario Tennis, Donkey Kong TF and Hyrule Warriors DE, and thats with early January Direct while we still need to have 1st Direct this year where we will have new announcements in any case. Nintendo published games directly effect on sales, sales proves that, sales in 2018. until September were slower because they were not big new releases, sales explode with Mario Party, Pokemon Lets Go and Smash Bros. Comparing effects of releases on hardware sales of console thats in its 6. year on market and console that yets need to enter its 3. year on market dont make any sense, because buy that time consoles are near and of its life cycle and every console entered in lower sales years compared to previous years in any case.
That's why if 3DS ends around 78-79M sold lifetime, i expect Switch around 85-90M by the end too. Switch is going to take the advantage this years, but like 3DS after 3rd year, is going to drop a lot, for Switch it will be 2020, and in 2021 probably will be a below 10M console per year console by then.
I think i already said how much i expect Switch doing
29'5 at the end of 2018
17M in 2019 -> 46'5M LT
12M in 2020 -> 58'5M LT
9M in 2021 -> 67'5M LT
7'5M in 2022 -> 75'0M LT
7M in 2023 -> 82'0M LT
and from there a few million more until stops around 87-88M.
That's a very specific and very difficult prediction to make, so i will be most probably wrong, but it's the pace i'm expecting. I know this crashes with every Nintendo fan here expecting Switch to sell more than 100M but this is my honest prediction, and it's based in the same reasons that made me believe 9-10M were going to be shipped in Q3 and the same reasons i was sure Switch was not going to reach 20M this FY.
Software sales, is different. I think the people expecting every IP from Nintendo selling the best ever on Switch are going to be right in the end. I said months ago i expected Smash Bros ending around 16-17M, but now is very probable it could surpass that, although i still think selling 5-6M more after such a huge launch is still a difficult task.