OP, I'd suggest you get a Switch if they're really a toss up to you. This thread is full of bad reasons why, as follows:
More exclusives - this is highly unlikely. The Switch is Nintendo joining the x86, single screen, dual analog herd. Any 3rd party game will be an easy port to PS4, XB1, PC, and many even to iOS/Android. Trying to draw parallels between it's potential future lineup of exclusives with the 3DS is a fools errand, especially when we've seen one of the headliner 3rd party exclusives (Monster Hunter) already jump ship.
More diversity - this argument requires you to ascribe some sort of magical uniqueness to Nintendo's games but not to all the unique titles from other studios. Nintendo has Mario. Sony has Bloodborne. Nintendo has Zelda, Sony has Horizon. All great games, all unique standout games.
Portability - this is absolutely subjective. Some love it, some have no use for it. That is your call but remember that regardless of where you land on those two the performance hit relative to hardware cost is something everyone receives.
Now as to the good reasons why you, specifically, should get a Switch instead:
1. You said you already owned a PS4 up until a few months ago, so I assume you got a pretty good dose of the exclusive highlights. If you disagree with that then re-evaluate the PS4, but I'm assuming you played as much Bloodborne, Horizon, Nioh, Persona 5, Yakuza, etc. as you were in the mood for then. You aren't going to be more likely to play games you already passed over once just because you spent even more money to play in that ecosystem.
2. The PS5 is probably 2 years away on the high end, and will almost certainly be backwards compatible. So you can basically view the next couple years of Sony content as your content bridge for the PS5. Better yet, given that the PS4 Pro and boost mode are real things it goes to reason that the PS5 will play all PS4 games at Pro levels or better, so you'll get the best experience possible with those games.
3. The flip side of post #2, the Switch isn't even a year old yet and is rapidly outselling the Wii U or even 3DS at this stage. It's all but locked in to be Nintendo's primary platform for the next 5 years at a minimum, likely their flagship platform well into 2023 or 2024. That's a lot of life and therefore value for your money.
4. The Switch has a backlog of games you can dive into right now that'll give you something worth buying the system for, right now. I'm talking Zelda, Splatoon 2, MK8, Snipper Clips if you like co-op games, etc.. Lots of good exclusive content available to justify the purchase today. On PS4 you'll be waiting for holiday exclusives, next year's first party exclusives, etc.. If you have a nice gaming PC are you really going to be starved for games to play in Q4 2017 and Q1 2018? Doubt it, by the time you'd likely get around to that backlog you'll be another year closer to PS5.
Just my two cents evaluating your specific situation.