The specs you provide to make the decision are not complete, so may be hard for a fair comparison.
Depends on what you are doing, are you traveling a lot? Work computer? Just a home desktop replacement? What type of work will you do?
I think for a purely work computer where your IT department uses Windows, or if you're only doing very basic stuff like internet/mail -- then use Windows laptop.
But for pretty much everything else, the Macbook would be better and will stay relevant and productive longer.
I believe that the Macbook will be faster and stay faster longer -- the iOS upgrades are great. Lots of apps, iOS development for iPhone/iPad. The free software for movie, music making. Lots of productivity apps. The communications including wireless will work better. It's a better integration of components and the software is faster. User interfaces are easier to understand. Windows is still changing a lot and the new 8 has lots of potential across many device/platforms.
But I have had a Dell i5 (14 in) ultra book. My mistake may have been upgrading to Windows 8. Once I did that I had nothing but problems with wireless constantly dropping out -- the graphics apps seemed slower than Windows 7. When I upgraded to Windows 8.1, it worked a bit better, but still drops out wireless -- tried all of the recommendations and ended up getting a USB wireless stick.
For most of my work, I go back to my iMap desktop. It's a few years old now, but still runs really smooth. I use it for everything, except I did have problems using my VPN connection at work, because the IT department doesn't support Mac. There are ways around this of course.
You get a lot of pretty nice software with the package.
