Vita because it has much better games than the 3ds.

Both sucked hard compared to their predecessors. The 3DS at least has a decent library but I hate the machine. The Vita has a garbage library but the machine is great.

I owned the Vita. I choose the 3DS. I am still getting that burn off my back.

3DS quite easily for me as it simply has a bigger, better gaming library. The Vita was still really impressive though and earned the title of indie machine until the Switch took over there. I picked one up last year with a few games which I've all really enjoyed but I personally have a tough time finding many games I actually want to play on it (without spending a large amount). 

The Vita suffered from both the N64 problem of using proprietary storage that raised prices and no one wanted and from the rise of mobile gaming. Then Sony stopped supporting it, essentially killing its library. Nintendo had infinitely better support for the Wii U which was in a similar position sales-wise. It's a shame because the hardware itself was great.

In terms of libraries it's no contest and really not fair. A Link Between Worlds, the Zelda 64 remakes, 3d Land, MK7, Kid Icarus, Fire Emblem Awakening and Echoes, Monster Hunter 3 4 and Generations, Pokemon, Resident Evil Revelations, Metroid Samus Returns, Luigi's Mansion, Yokai Watch, Bravely Default, and the list goes on. It's not fair to compare a system with a widely celebrated lineup to a system whose lineup consists of hand-me-downs from the home consoles and indies.

I never owned a Vita, but there wasn't anything compelling for me to own one. 3DS wins for me

This was one of the first ultra long arguments I had on videogame forums. I was on a forum called listranker or videogameranker or something like that. It was late 2012 and Vita was already borderline dead. I just could not understand for the life of me why some people genuinely thought Vita was better. I still can't. 3DS has it all. Better price. Better games. Backwards compatibility. More screen real estate. Folds into itself. The only thing Vita has going for it are graphics, but even that's a stretch because 3DS has 3D mode which IMO adds way more to games than any other graphics feature. Not to mention that graphics are meaningless if the price is too high.

Vita has 59 games on metacritic rated 80 or above, with most of them being multiplatform games. 

3DS has 93 games on metacritic rated 80 or above, with most of them being unique to the system.

I have over 30 3DS games, and I don't buy ports or indies for it.

If I built a Vita collection I'd have to ignore that pretty much everything is on PS4 now. And even then I'd only wind up with 13 games I really wanted to play.

I had both and the 3DS library can't be denied. However, if both released right now, I'd get a Vita first. It had so many features that even the Switch can't touch.

Bluetooth, free online, cross game chat, back touch screen, themes, web browser, camera, music, apps like netflix, etc. I spent more time using the features than I did playing games.

3DS has a better library, so it's 3DS.

Hah, what a match up. This is like if the US would play Gibraltar in an all-star American Football match.

I have both these systems too actually. I got the Vita, for which I had to scour heaven and hell already to find back in 2015, because I wanted to play Uncharted Golden Abyss. A little afterwards I got Resident Evil Revelations 2 on it because I thought it would be fair to get that game on a handheld due to Revelations 1 being a 3DS game. Uncharted was fine, actually better than like say Lost Legacy, but Revelations 2 sucked. After that I never got any other game. If there ever was a system where the trope “it has no games” was applicable it is the Vita. There’s literally nothing else I wanted to buy and nothing else that even remotely interested me. I also wasn’t exactly fond of the hardware either because it was way too heavy to comfortably hold for a longer period of time, the useless back touch pad was in the way making me cramp my hands and I was never impressed by its graphics. For all its supposed power the two games I had didn’t look better than what 3DS had to offer, on the contrary. Lastly, my PSN was hacked like two weeks after I got it. Really, Vita is in the lowest region for me.

Meanwhile 3DS was great. One of the best systems there is, and perhaps the best handheld. It has plenty of games that made it to my list of favorites. To keep the comparison with Resident Evil, Revelaitons 1 was amazing, and looked a hundred times better. The 3D effect was a hit with me personally, because I could better judge distances between objects in games, most notably I got much better at jumping gaps for example. It even made me worse at jumping gaps in games on other ‘flat’ systems. It’s kind of sad that it is gone now on Switch. I ended up with a sizable collection of games over the years. The 3DS still has games I wanted but never bought, and I still haven’t finished a lot of the ones I own. There’s really only one downside about 3DS; with Triforce Heroes is has the questionable distinction of being home to the worst Zelda game.

So yeah, in case you couldn’t tell yet, 3DS with the biggest of landslides.