I’m in your boat; I never owned a PS3 and was sceptical about getting a PS4 when the Xbox 360 had been so good to me. However I will be still after the no more used games stuff because...
PRICE - its $100 cheaper/ £80 in the UK that's a pretty significant difference. Even if you factor in the PS eye (sold separately at $60) it’s still $40 cheaper, and you have the option where Xbox pretty much force you to get it
PERFORMANCE - if you know your PC stuff you'll know this. The specs on the PS4 are simply better in RAM, CPU and the graphics card by quite a bit. This will effect PS exclusives the most making them look significantly better than the Xbox ones (check out kill zone and infamous for an idea). but it may effect normal games too as both systems are PC like and thus easier to develop for and change setting meaning you could for example see better frames or lighting on the PS4.
CONTROLLER - while different to the Xbox's (put me off initially) it does come with great features eg the touch-pad which can be used for web browsing with ease. The stick layout you’ll adjust to within days and really wont effect you much
EXCLUSIVES - I like HALO but that's just about the only good one Xbox has whereas on PS there are infamous, uncharted, kill zone and much more. The difference is these developers are very skilled and supported by Sony. Naughty dog for example made "uncharted 3" and the new "the last of us" both of which earned 10/10 from many reviewers which is VERY rare. The new Xbox exclusives may look ok but we have nothing to put to their name.
PLAY STATION NETWORK - while inferior last gen to LIVE this gen its certainly stepped up its game as it now cost meaning better quality network, dashboard updates , apps etc. putting it on par with Xbox LIVE. BUT wait! With PS+ you get LOADS of added benefits like free games (and i mean new proper games too) as well as an online personal library, early beta access's more, making it now seem superior to LIVE. Also it’s cheaper
there are a lot of other nifty little features that make it better too (user interface, game recording , taking over o friends game or live watching him play, switching instantly between games and the store and the home screen and apps) but these are the main ones. the only things i can think of that Xbox has over it is TV (which you can do by pressing your remote) and Kinects likely superiority over "eye" so unless you’re an avid yoga person id get the PS4, they seem to be really focused this generation and care about the gamers and won’t try to **** us over like Microsoft did with the things they've just dropped
don’t believe the misconception that Xbox is games + entertainment and PlayStation isn’t , it can do all those thing like Netflix and movies (Sony make films !) it’s just more focussed on games which you wand if you’re going to be spending so much money on. I’d really recommend the PS4 they've fixed all problems last gen and more, don't stick with Xbox just because the 360 was good.