I finally now own both the Xbox One and PS4 and have some thoughts about them. Please keep in mind this is only my opinion and not saying it really means anything. :>
I guess I can start with how each looks as there is a pretty big difference. The Xbox One is a medium sized heavier square box with a big, some people call it a brick, power cord. Nothing fancy, but a lot of venting and fans so it does the job. The PS4 looks a little sleeker with a smaller tapered look, much smaller lighter with a normal power cord. I like the look of the PS4 better now that I have seen it in person, but overall if in an entertainment unit, it really doesn’t matter, but if on a desktop, it might matter more and the PS4 does look a little better.
The controllers are next, again there is a pretty big difference between both. The Xbox One controller is one stick and directional pad, it works well and fits in your hands very nice. It is a little larger and heaver than the the PS4 controller and it's noticeable sometimes especially if your switching back and forth between the two systems. The PS4 controller has a different dual stick layout, small touchpad area and built in speaker. It also allows the use of any headset with a standard 3.5mm jack, no adapter is needed like the Xbox One controller requires. The Xbox One controller is rock solid like anyone that has used one knows, but I am sort of liking the touchpad and speaker of the PS4 controller. It might not sound like much, but when a game utilizes the controller speaker or touchpad it really adds a lot. I still get a kick every time a sound comes out of it, but again that is just me.
The all important games are a big question. For my taste, I find both systems have some stunning and fun games. Each one has both big hits and misses, but I don't think either really has an edge to better games, especially when looking at upcoming games thru the end of the year. I found the PS4 with PS+ does offer a few more freebies and demos, but the Xbox One and Live has some too. I have no real brand loyalty to any "exclusives" like Halo, Kill Zone, etc... so no game or even couple games is going to make any difference in the choice of systems for me. If your someone who must have one of the "exclusives" then nothing about the other system is going to change your mine and your locked into the system it's on.
Next thing a lot of people ask me now that I have both systems, which has better graphics. The real answer is both have amazing graphics, but a lot can depend on the game. Both have games that will amaze you and both have only so so games. If I really had to pick one, I would probably have to say the PS4 has a slight edge.
UI, apps, kinect, snap window and other included things. I am condensing this so not to be overly long. For the "who has the most of this and that", by far the Xbox One does. More apps, more features, more elaborate UI, more TV features, etc.... but one caution is at this time not all of them work well. The kinect and TV features on the Xbox One I found so frustrating and buggy I removed my kinect and do not even use any of the TV features anymore. The snap window on the Xbox One is neat, allowing you to play a game and do something else or really do any two things at the same time. The PS4 does not have as many features and is more streamlined with a simple UI, only a handful of big name apps, but was designed that way. What is better depends on personal preference really. Do you prefer everything and the kitchen sink or do you prefer simplistic with just the basics, that’s up to you.
Another thing I have been asked a lot owning both systems, is which I prefer or think is the better system. I really don't think there is a solid winner, it depends on what you want. If you want possibly the slightly better gaming system, don’t care about apps, TV stuff and all that, I would say go with the PS4. If you want a lot of everything and some great games too, go with the Xbox One. I really see the PS4 more as a gaming system not an entertainment system like the Xbox One is trying to be.
The future and bottom line is, which one you will prefer all depends on your own preferences and needs. Both are great systems with stunning graphics and fun games. Who knows what the future holds. Microsoft seems to be adding anything and everything they can with updates all the time so chances are better the Xbox One will add/have it and have it first if Sony even ever adds it. Sony seems to be more concentrated around gaming, but if they wanted, they could pretty much make the PS4 do everything the Xbox One can, except the TV stuff with the pass thru, with just an update or two. So the future could be very interesting.