Raw numbers have lied about real performance since the 8-bit days, so that won't do you any good.
It also is not a constant in terms of the output we see. The PS2 is an excellent example of how inferior hardware can produce comparable results due to far more development priority. Developers really worked to maximize everything the PS2 could do and found a lot of advanced tricks to that end. Meanwhile the Vita and Wii U are likely two systems that punched well below their actual weight due to lack of life cycle and developer interest.
Analogy is probably the best way to understand a system's current horsepower, and ideally with as few additional fixed variables (developers, release window, etc.) as possible.
Thankfully we have a great example with Breath of the Wild. Both made by the same Nintendo development team. Both released at basically the same time. I'd probably give a "pulled from my buttocks" frames per second "average" (i.e. what you'll experience by just playing the game, not stress testing specific areas) on each respective version (Wii U, handheld Switch, docked Switch, later two post patch) at 24 FPS, 29 FPS, 27 FPS.
Now if we just play along and say those are roughly accurate average estimates we can calculate pixel throughput per second, as follows:
Wii U - 720p or 921,600 pixels per frame x 24 frames per second = 22.118M pixels per second.
Switch Handheld - 921,600 pixels per frame x 29 frames per seond = 26.726M pixels per second, a roughly 20% increase in pixel throughput.
Switch Docked - 900p so 1,440,000 pixels per frame x 27 frames per second = 38.88M pixels per second, a roughly 45% increase over the handheld mode, and a 75% increase over the Wii U.
For comparison the PS3 v. PS4 versions of The Last of Us were:
PS3 - 720p (921,600 pixels) per frame x approximately 27 frames per second = 24.883M
PS4 - 1080p (2.1M pixels) per frame x 60 frames per second = 126M
So a roughly 500% increase in pixel throughput from an end of life game ported to new hardware.
*DISCLAIMER* Not all frames are rendered equally. This does not work on a game v. game comparison. These examples used here are to show the difference in performance between the same game from one generation of hardware versus it's next generation release.
So with that out of the way, you can see where a claim of the PS4 being 5 times more powerful than the PS3 is something you can meaningfully back up with math.
The Switch versus the Wii U however shows that the system is much closer to it's predecessor than what we typically associate a generational transition with in the console space.
That is a direct product of the fact that the Switch is not actually the Wii U's direct successor. It is more the successor to the 3DS but design in such a way so as to allow Nintendo to merge their two markets (handheld and console) onto a single platform. Some in this thread have stated that Switch games will perpetually be held back by the handheld mode demand. While technically true, games will be designed based on an acceptable performance threshold in handheld mode, that isn't really holding the games back in my opinion. To me the Switch is much more like buying the latest Nintendo handheld and getting the Switch "Pro" for free via docked mode. This is even more relevant than the PS4 to PS4 Pro or XB1 to Scorpio upgrade as handhelds are traditionally not designed to be capable of outputting a native resolution worthy of being displayed on a TV screen. The Switch solves that out of the box.
I once said on this forum that to me the Wii U wasn't under powered as it delivered all the horsepower needed to deliver Nintendo's artistic vision. Zelda: BotW has made me recant that statement completely. If that is indicative of Nintendo's new level of output going forward I seriously question if the Switch is up to the task. Despite that however it is still the single best hardware offering Nintendo has presented to us since the SNES. No gimmicks like the Wii U tablet or Wii motion controls. Not missing the boat on key hardware features like they did with both the N64 and GC media choices. Not asking contemporary hardware MSRP for clearly aged tech like with the NDS or 3DS.
I loved most of those systems, but the successes were the result of software carrying otherwise questionable hardware across the finish line and the failures were almost always directly tied to their poor hardware choices. The Switch avoids any of the later that I can readily identify and therefore opens the door for the software to carry it.
It is the most powerful gaming dedicated handheld ever made, think of it like that and not as a quarter step into the current generation that it would be as a console, because doing anything else misses the real value in it's design.