The Last of Us.

I don't think you can go wrong with either choice... If you can only afford one though, I'd probably go with Dark Souls II, since it will probably give you more hours of gameplay. 

Go in on The Last of Us first.

DSII is solid, but it's more of the same for you... And it's the weakest of the Souls games (thanks to being made by the B-team while the A-team and Miyazaki rejoined with Sony for Bloodborne after Dark Souls 1's DLC was finished).

Plus, you can get into DSII later down the road with the Scholars of the First Sin edition.

Get The Last of Us. Scholars of the First Sin releases later this year - get that then.

last of Us

The Last of US

ok thanks for the tips guys, I'll be getting The Last of us!

Easy: TLOUR

Prepare to be astonished.

You should've created a poll to make it easier xD

I'd suggest The Last of US.  Seeing as how it's won so many awards and some are coining it as Game of the Decade (not going to quote anybody), you deserve to experience why that game's been highly praised.  You've already played Demon Souls and Dark Souls, so you alread have a general idea of what to expect when playing Dark Souls 2 anyways so why not try something different.

DS2 is better, but if you played the other DS, the overwhelming feeling of disappointment over it's quality by comparison to its predecessors will probably ruin the game for you. If you haven't played TLOU, while it's pretty overrated, it's still good and one of those games everyone has to play to be a part of the general gaming discussion. Plus the PS4 version runs at 60fps, which is nice.

If you never played a Souls game, I would have said DS2 (actually, I would have said to wait a few weeks and buy Bloodborne), but since you've played them, you'll do yourself a service to play TLOU, because it's one of the most important games of the last generation, if nothing else.