I don’t see why you’re comparing it to last year’s 13" MacBook Pro.
The new 15" MacBook Pro has specs that are very much like this DELL laptop. Same screen size, same resolution. Same SSD, RAM, and GPU. The MBP has a slightly faster CPU, i7 2.3Ghz instead of DELL’s i7 2.2Ghz. The DELL is 10% cheaper.
The 15" is slightly less DPI. I was only comparing DPI because, to be honest, every laptop I've ever used that wasn't a Thinkpad or a Macbook has left me wondering whether I should just use pen and paper instead.
The DELL has a 15.6" screen, the MBP has a 15.4" screen. The screens both have the same resolution and aspect ratio. That means the MBP’s screen has a slightly higher DPI (221 versus 218).
They don't have the same aspect ratio. The Dell is 16:9 while the rMBP is 16:10.
They don't have the same resolution either. The rMBP is 2880x1800 while the Dell is 3200x1800.
Not even an option worth considering, IMO. And that's with 10+ years experience with Debian/Slackware/Arch that I'm saying that. I've run the above as my primary desktops for years but they still aren't ready for primetime (for both getting work done and for entertainment). That goes triple for laptops.
I was dragged back to the Windows world with Vista and 7 because it was obviously more efficient with my time. Last year I purchased a mac mini and it has completely taken over as the machine that I get all of my work done on. Easily five times more efficiently than any other platform. My Windows machine does nothing more than store media and play games. The next computer I buy is going to be an rMBP, I have no doubt.
And before someone eventually brings up Ubuntu, it's a joke and a toy OS that's suitable for hobbyists and old people. I wouldn't suggest it to anyone who wants to actually learn Linux.
A fresh install of MacOS is probably 90% of the way ready for me to do everything I need. Getting it the other 10% there takes less than 2 hours. Tops.
Windows (any flavor) starts at maybe 30%. Closing the gap is easily a full day.
Getting a Linux system up and running properly takes a weekend, taking time to do everything the right way. It's worth it, no doubt, but requires much more effort to properly administer. My time is way too valuable for that.
I think it depends on proficiency with the platform more than anything. I've spent 8 out of the past 10 years with Linux as my laptop platform, the other two were split between Windows & MacOS. Both of those were huge productivity steps backward (big enough that 2 of those Linux years were from running Linux on a MacBook Pro!!). Ironically about half of the productivity loss was due to increased administration time. The only real win with the other platforms was somewhat better battery life.
The new 15" MacBook Pro has specs that are very much like this DELL laptop. Same screen size, same resolution. Same SSD, RAM, and GPU. The MBP has a slightly faster CPU, i7 2.3Ghz instead of DELL’s i7 2.2Ghz. The DELL is 10% cheaper.