Good read from The Verge. Some choice quotes from the article:
You probably know the broad strokes: the PSP was overshadowed by the hugely popular Nintendo DS, while the PS Vita never took off at all. And now we have the Switch.
But it would be unfair to write off Sony's travails in the portable gaming industry. The PSP and Vita were not only innovative devices in their own right, but the most daunting competitors Nintendo ever faced in the handheld space. They're more than just a footnote in the PlayStation story.
In hindsight, when the games industry was worried about what mobile gaming might do to traditional consoles around the turn of the decade, it only really applied to Sony portables in the end. Their extra features became redundant next to smartphones; popular genres shifted to commute-friendly free gacha titles; and Sony's technical advantage was quickly lost to phones that got better and faster every year.
This is sad to say because of how impressive Sony's handhelds were in their day. But perhaps, after these two and a half decades of Sony and Nintendo trading blows, each company has arrived at its most natural position. Nintendo is so focused on making the best portable console possible that it's supplanted its own home console business altogether with a simple USB-C dock, while Sony has achieved great success with the PS4 simply by focusing on games. It's hard to see either company straying too far from its path any time soon.