It would help a lot if you could give more specific models so we could look up details How about a URL to the units you are comparing.
the dell seems to only offer a gtx 1050 4gb, while the razor offers the gtx 1060 6gb. the gtx 1050 TI version is the typical go to option for premiere and a 4-core laptop cpu, but the non TI version should still be ok for premiere and good for photoshop. the gtx 1060 6gb in the razor gets into overkill territory for a 4-core laptop cpu and might run up the price.
i'm not sure about the difference in displays for the two laptops. a quick search and look at some reviews show positive things about both, and suggest both have high 99-100% srgb coverage. you may want to search for reviews on these laptops to see what they have to say about the displays and if any review finds something bad.
Narrowed to the two choices you provide, I'd vote for the Dell option. It's difficult to build a reliable, solid thin, light and powerful laptop and the latest XPS-15 is the latest in a line that has been doing that for years now.
While I haven't personally owned an XPS branded Dell, I've owned numerous Latitude and Precision Dell laptops over the years. And one, a Latitude 15" model that I had three years ago had a VERY subtle problem with the heat pipe cooling system tolerances that was causing intermittent crashes particularly when the GPU was working hard. The problem had to escalate levels past Dell's rather worthless first line support to discussing my problem with a Sr. tech in Texas. Then, after that it didn't take long for this problem to be resolved. And while they could have fixed the problem - once we new it was a problem with the heat pipe insufficiently coupled with the GPU - the Sr. tech chose instead to have an on-site repair tech replace the entire motherboard and heat pipe cooling system so that they could get the flawed parts back to Round Rock, TX. That way, Dell's engineering / manufacturing team could study the problem in detail and benefit future design / manufacturing / etc. by learning from this mistake.
Don't forget - If you've come from Apple hardware and support, you've come from the best and most other options are not as strong.
If I had to choose a laptop to do 4k editing on it would be bigger, heavier, thicker (best cooling comes from Dell/HP workstation and gamer laptop designs where you see two huge cooling ports on the back), and it would have 32GB of RAM and at least 2 SSDs. I'm not sure why you are leaving the Apple camp, but if is to gain more performance, then these two sexy, light, thin choices may not be the best. OTOH, if you are leaving the Apple camp to get something with similar performance and still be retaining a thin, light, laptop with a 4k display, then the models you've found seem like an excellent fit.
Also BTW, if I had to choose a laptop to run Photoshop on, the XPS-15 you link to above seems like a pretty awesome choice for that use case, and yes it can pull off 4k video editing albeit with some speed compromises when the need arises.
i'd review the 4k difficulties in premiere's UI small fonts. may not be worth it. I haven't heard too many good things about the xps screen lag as well. I'd be wary. Can you do a test drive from a friend or get a loaner?
First of all I'd like to thank all the people who answered to my post: sorry for doing that only now, but I wasn't able to do it before.
The intent of my question was to explore the pc environment to check an option for my Mac. Unlucky Premiere and After effects work better with Cuda by Nvidia, a missing thing in Apple computers. I saw some test made with Premiere, and telling true, the difference between Mac vs pc was absolutely embarrassing and with a fraction of the price and powerful hardware.
On the other side I perfectly know Apple environment, I haven't had any troubles with hardware (which is, in my opinion; better optimized than PCs) and the support is fantastic...More, even if Win 10 sounds to be stable, I'd need some time to master the system as I do with Mac....
So this is my trouble: keep Mac or leave for Win???? :-O
Have you bought XPS 9560? If so could you give your opinion?
I have the same quest to find new laptop right now...