I like a desktop for gaming or other intense use. I built the one I am using two years ago and haven't had a bit of a problem or lag. With all the parts, no software, it cost around $1,700 US to build. Laptops are fine if you need portability, but they tend to overheat, so use a cooler of some sort if you get one. With a good desktop, you can change out a fried graphics card if you have to, upgrade CPU, add fans or liquid cooling, and expand your hardware selection.
Here's what I have:
Intel i7 2600k CPU, unlocked
Asus P8P67 pro motherboard (AMD Crossfire & Nvidia SLI capable)
Nvidia GTX 560 Ti twin Frozer GPU
850 watt modular power supply
CPU cooler - heat sink & fan
8 GB RAM
Sound Blaster X-fi Titanium PCIe sound card
1 TB hard drive
Media card reader
DVD writer/reader
Blu-ray writer/reader
Full sized case with 4 fans installed, set up for adding 3 more if needed. Individual fan controls.
The motherboard, CPU and GPU can be overclocked if I want to, but so far I haven't seen a need for it.
Alienware is just a fancy (and expensive) Dell computer. There are other gaming laptops on the market. If you want to get one, look around on Google to compare features and price. The gaming laptops are all pretty expensive. A desktop will cost less, have a bigger screen and will probably be more durable.
Unless you really need the portability, I'd go with a good desktop. You'll have a bigger choice of components and monitor size, and a more durable machine for the money. I just did a quick search, and all of the laptops I saw were at least as expensive as my desktop; many of them were much more expensive. You can put the money you save into a beautiful monitor, back-lit mechanical keyboard or programmable mouse.
Your ENB and/or mod choices will be dictated by the quality of your computer, and particularly your GPU and sufficient RAM.