I'd say its not a cut and dried decision between laptop and desktop, and that it depends on your needs and patterns of use -- the price, power, or cost-effectiveness of hardware really only enters into it as far as it either drives your needs or budgetary limitations.

For me, I want a relatively-powerful computer that I can move around and be comfortable working on when necessary, and I want to use that same machine with better amenities when I'm working at home. As such, I have a high-end Lenovo laptop (W530), which is pretty much maxed out, and a dock that supports USB 3.0 and three high-resolution monitors. For what I spent, I could have built a more powerful desktop workstation -- or, I could have built a similarly spec'ed desktop for probably half the cost. Why didn't I take one of those options? Because I value being able to take my working environment with me when I need to be mobile, or just want to spend an afternoon setup in a coffee shop somewhere.

Although there are people who really need all the power that can be crammed into a desktop computer that would not be well-served by *any* laptop, and there are those who's budgets are so constrained that they simply can't afford the premium that portability demands while still getting a decent machine, most users fall somewhere in the middle, and can be well-served by either desktops or laptops. Obviously, portability will cost more, but if you're in the middle group you can choose the balance of power and affordability that's best for you.

Most people don't need 6-8 CPU cores, 1000w PSUs, Triple-SLI with 13" GPU cards, or 6+ hard disks. Few actually do, though many more think they do. Honestly, if external GPUs were more practical right now, I'd invest in one of those and a good NAS, and probably never buy another desktop computer again. As we're not quite there yet, if I build up a new gaming rig this fall (seeing as the laptop takes care of my work needs), I'm going small-form-factor: Haswell ITX board, a compact 550w PSU, a couple fast 2.5" SSD drives, as much RAM as the board will take, and as large a single GPU that the PSU will feed and will physically fit inside the case. The older I get (or perhaps, the more I move between residences) I keep finding that less (stuff) is more.

my alienware m17x has 6 usb ports 3 external monitors 2 hard disks

and never gets hotter than 80c even after 24 hours of stress testing

I can open the case in 30 seconds and replace any main component in minutes

it has a quadcore i7 and GTX660

and was cheaper than equivalent PC + UPS

I never look at the built-in monitor

and it uses 1/6 the power of my last desktop

also the economies of scale are with laptops now

my alienware m17x has 6 usb ports 3 external monitors 2 hard disks

and never gets hotter than 80c even after 24 hours of stress testing

I can open the case in 30 seconds and replace any main component in minutes

it has a quadcore i7 and GTX660
and was cheaper than equivalent PC + UPS

Those are good points, but there are a few things to consider.
You night be able to open the case, but good luck finding an upgraded gpu or CPU for your machine.

Also your i7 and gtx are almost certainly mobile parts, so you can't really compare the prices

It makes no sense to "upgrade" a PC

because paying for 2 CPUs or 2 GPUs but only using 1 is throwing money down the drain

What makes sense is to build a machine at the price/quality/performance sweetspot, load it with RAM and don't tinker with it

The market for desktop PCs is now tiny - laptops now outperform desktops on price/performance

When you factor in the UPS laptops are the only choice

It makes no sense to "upgrade" a PC
because paying for 2 CPUs or 2 GPUs but only using 1 is throwing money down the drain

What makes sense is to build a machine at the price/quality/performance sweetspot, load it with RAM and don't tinker with it

The market for desktop PCs is now tiny - laptops now outperform desktops on price/performance

When you factor in the UPS laptops are the only choice

dude....are you high?

Your linked PC components are not fairly balanced at that prize range.

I did a build list for you, it is $17 more, but has better power supply, processor, video card, heatsink, SSD and HDD. Plus cheaper RAM.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD FX-8320 3.5GHz 8-Core Processor ($149.99 @ Microcenter)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ Outlet PC)
Motherboard: Asus M5A97 R2.0 ATX AM3+ Motherboard ($94.99 @ Microcenter)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory ($59.99 @ Newegg)
Storage: Samsung 840 Series 120GB 2.5" Solid State Disk ($93.99 @ Adorama)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($65.98 @ Outlet PC)
Video Card: Gigabyte Radeon HD 7870 2GB Video Card ($234.99 @ Amazon)
Case: NZXT Source 210 (White) ATX Mid Tower Case ($39.99 @ Amazon)
Power Supply: SeaSonic G 550W 80 PLUS Gold Certified ATX12V / EPS12V Power Supply ($79.99 @ Amazon)
Optical Drive: LG UH12NS29 Blu-Ray Reader, DVD/CD Writer ($39.99 @ Newegg)
Operating System: Microsoft Windows 8 (OEM) (64-bit) ($87.98 @ Outlet PC)
Total: $977.86
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-06-24 15:12 EDT-0400)

I noticed that you already bought your items, my condolences.

if you use your PC for anything important you need a UPS

once you factor in the cost of a UPS

it is usually cheaper to buy a laptop - they have very good UPS built in ...

modern laptops have powerful enough GPU to play GTA4 BF3 etc with decent settings

they have room for 2 or 3 hard disks and can support 3 external monitors

they use little power and make little noise

buying desktops just doesn't make sense any more

On the contrary. Laptops are "kind of acceptable" when you need a computer on the road. This is little surprising, since that's what they're made for, too. As compared to "no computer" they simply win. Otherwise they are overpriced and simply pathetic.

The difference in performance between a laptop and an equally priced desktop is not somewhere around 20% or 30%, but rather around 8-10 times. It's even more drastic with what are they called... ultrabooks, convertibles (that is, tablets with an attachable keyboard)?

My 4 year old 2.6 GHz desktop (which is already rather slow compared to its more recent brother) runs at approximately 5-6 times the speed (wall clock) as compared to my 1.8 GHz Atom convertible that costs as much as that desktop did 4 years ago.

And then of course those tiny screens...

An entirely sufficient UPS (which will give you around 20 mins) costs under 100 euros, by the way. It's not like you need UPS for 12 hours. If you're desperate on saving money, you get one for half as much money too, which is still sufficient to do a proper shutdown without data loss.

The difference in performance between a laptop and an equally priced desktop is not somewhere around 20% or 30%, but rather around 8-10 times. It's even more drastic with what are they called... ultrabooks, convertibles (that is, tablets with an attachable keyboard)?

Hyperbole much?

Please show me how to build this as a desktop for < $200.

http://www.xoticpc.com/sager-np8250s-clevo-p157sm-p-5870.html

My conclusions after 8 years of computermerizing is that any laptop with desktop-like performance is not going to really be used like a laptop because even if it weren't trying to melt the universe one direction at a time, it would be running out of battery in five minutes anyway.

Plus more than one monitor feels like a necessity at this point.

The difference in performance between a laptop and an equally priced desktop is not somewhere around 20% or 30%, but rather around 8-10 times. It's even more drastic with what are they called... ultrabooks, convertibles (that is, tablets with an attachable keyboard)?

Hyperbole much?

Please show me how to build this as a desktop for < $200.

http://www.xoticpc.com/sager-np8250s-clevo-p157sm-p-5870.html

What about that? I see "starting at $1750", not "<$200". Mind you, "starting". Not worth reading any further.

For $1750 you get a beast of a desktop. One that, regardless of colorful advertizing and buzzwords, performs a task in 1 second that takes 10 seconds (wall clock time) on an equally priced laptop.

Dude, do not try to kid me, I see this every day. My wife works home office for the Devil, and every task that I can perform "instantly" on my home desktop (which is not the most powerful nor most recent machine), no matter how trivial it is, takes 5-6 times as long. My work desktop has about 2.5-3 times the horsepower as compared to my private one.

Telling someone that a laptop is as good as a desktop (except for the special case of needing a computer on the road!) is as ridiculous as claiming that Windows 8 is better than Windows 7. This simply defies reality. Yes I know you work for Microsoft, no thank you, not interested in how awesome it is.