Ok this is my technical understanding...
The PS4 is basically like a harder top speed but isn't integrated as tightly as the Vita, the PS4 is basically just reflecting, a big collapse of Sony in a large strain of the PC-ification of the gaming industry. It's essentially just a PC, and so it doesn't do what consoles have done more effectively than the PC which is to have integrated components.
The Vita does have this, in addition, it has the OLED screen and other novelties that make it technologically superior IMO, not in all respects, a clock speed is a clock speed, ram is ram, and all that, but it seems to be the way it was built it was like a panzer tank but with guns pointing every direction, and not necessarily fewer weapons all pointing in the right direction.
As far as I can tell, load times, basics of functions, on and off, all those elements are faster on the Vita, furthermore, games that take full advantage of the OLED screen look pretty amazing.
On the PS4 side, yes, there are a handful of interesting PS4 exclusives, but I think those cater primarily to established demographics and such. Maybe FFXV is the first FF for someone, but it certainly isn't my first FF, and consequently I would just be there to enjoy something I already kind of know and like, not necessarily to go deeper into it.
Moreover, at this point, almost every other major console exclusive is being ported to the PC, including as I mentioned in the other thread, Nier 2, etc.
So in short, The PS4 and Xbone are simply, machine wise, and also with respect to the games, have become part of the larger PC umbrella, there isn't much to be gained from owning one aside from, as I said, support for particular franchises (which is fine and dandy).
Moreover, those franchises tend to be more established, and while of course can be quite fun, I don't think for instance, something like FFXV is quite as unique or interesting an RPG series as perhaps a Ragnarock Odyssey (not really a Monster Hunter fan, myself)
But the Vita, I think alludes to the point when gaming is about making unique technological progress and stuff, so consequently, I'd say it's in much better shape.
Anyway, I don't think any hardcore Sony or RPG fan can go wrong, it's basically like Genesis 2.0, or Dreamcast 3.0, it's the good system that really is good that never catches on with the greater group because raisins.
Now, as to getting one now, it's a bit tricker, as you say, the support has dropped off, but I've heard that's because they feel 3rd parties are adequately supporting the system.
I think the reason for the Vita's struggles is, quite simply, the 3DS. That is to say, most people have just adopted the 3DS over the Vita, so it's not really, mobile, or whatever that's causing the problems, it's just that the 3DS has been a super impressive system. '
Final edit: I think ultimately the true answer is simply... 3ds... lol