I got a Switch in July 2017. I got a PS4 (the pro version) in July 2019.
First-party is better on Switch. Very few could come up with a compelling argument otherwise. But third-party titles are better on PS4. Not only do you have a lot more AAA games, but you have plenty of smaller scale games and indies as well. I know Switch has a ton of small-scale games and indies, but the PS4 still has a good amount.
I mostly play games offline, but PS Plus is far superior to Nintendo Switch Online. Not to mention the option of PS Now. I've never tried PS Now, but it's a valid option for PS2, PS3, and PS4 games.
And of course PS4 can do a lot more besides gaming. DVD and Blu-ray movies, far more video apps, and even a simple internet browser.
PS4 and PS4 Pro are much better in specs and as a multimedia device. Though admittedly PS3 was a superior multimedia device. And portability for the Switch is a great option, though one I don't often use.
I will admit PS4 has the benefit of almost 7 years on the market. Switch has only been out for about 3.5 years. Maybe my opinion will change, but PS4 is the superior platform to me at the moment.
TL;DR PlayStation 4 is the best.
Lifetime Sales Predictions
PS4: 130 mil (was 100 million) Xbox One: 55 mil (was 50 mil) Switch: 110 million (was 73, then 96 million)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima