This may be a little long... fair warning..
First of all do I expect any of you to take my word that I am indeed a developer working with these systems? No...That being said read the following if you wish and take what you want from it. I was a frequent poster on these forums before programming became a career and as I was hired we were asked to limit the amount of time we spend on forums and obviously not post any information about our projects. I'm not willing to tell you the name of the project I'm currently apart of as I don't want my opinion to reflect onto the company I work for. To the good stuff:
The PS4 has been a dream to work on, it's easy and the dev environment is pretty mature considering these consoles have yet to launch. Sony has supplied us with some great drivers to work with allowing us to pump out 1080p games easier then on the X1. That being said, the X1'x dev environment still has some maturing to do. The software and drivers we've been given so far have been good, but not as well optimized as the PS4's and this is why you may see some games on the X1 in 720P or 900P compared to the PS4's 1080 but this will quickly change and 1080p on both consoles will be standard.. The PS4 dev environment will of course improve over time but does not have the amount of improvement room that the X1 has right now, I suspect the X1 will eventually pair up with the PS4 but never surpass... It almost feels as though the X1 was a little rushed and Microsoft wasn't quite ready to get a new system out this year... The esRAM has been interesting to work with, it is an evolution over the 360's option and we've been pretty impressed with the amount of bandwidth gained from taking advantage of this little cache. These consoles are very very close in terms of raw dev power and in my opinion the X1 will surprise some people. Tiled Resources is a new type of coding we have seen in Aplha on the X1 and it's going to turn some heads in the dev world. There's a reason the X1 was shipped with a 4K rated HDMI cord...Tiled resourcing will eventually allow us to take huge 4K textures and compress them down to 1080p sizes allowing us to pump out 4K res without taxing the X1. I believe we will see 4K content on these systems in the form of movies and maybe some small indy games but don't hold your breath on a 4K halo or 4K Killzone, the power just isn't there.
Overall it's refreshing to see some new hardware to work with as the 360 and PS3 were really starting to show their age. Both of these consoles are great to work with and their much closer in terms of performance then the general public seem to understand. The PS4 is just a pure powerhouse in the console world and you will see amazing things from it. We don't even come close to touching its potential and we thought our project was going to be somewhat demanding. The X1 is the same, taking advantage of the esRAM has really surprised us as we were dreading the idea of working with it at first.
My advice.. be patient...both of these consoles are going to give you guys some amazing visuals and experiences.. don't let fan boyism get in the way of experiencing both.