That's a very strange comparison.
1 is a home built PC, the other is pre-made. The premade one is 1.7times the price of the self build.
Also, you haven't specified what you intend to use it for?
As both are reasonably lent towards gaming, the 2nd will likely offer you better value and better performance in games due to better graphics and overclockable processor. If you are looking to do CPU intensive multi-threaded tasks then an i7 will probably be a better choice.
What would be better is if you specified if you want to self build or not, and what your budget is. A ~$1000 gaming machine build will likely look very similar to the 2nd link, but if you have $1500+ to spend you can get a lot more for your money.
I would say i5 just in the quality parts, plus better graphics of the ti from on ti. In gaming the i7 HT is not utilized, the corsair ram is better than whats in alienware, all prebuilts, psu is prob better, less hdd but who needs 2tb? lol
In price alone get the i5 custom built, the alienware case is pretty sweet but the components they put in prebuilts are just crap, if i remember right the 660gtx in the alienware is a 1.5gb instead of the standard 2gb, also im guessing the alienware uses stock intel cooling, but im not sure.
well wherever u can find the alienware case its prob gonna cost to much, so no lol go find a case u like in ur budget and the ram is actually $50 right now, the cost of ram has done up recently, to the point u can get 8gb of 1600 for the cost of some 2133.
That site with the best pc for $1000 is somewhat out of date as pricing difference but the ram and motherboard cost more than what the site says so id rebuild it and tweak it to fit ur costs, but i would def go the 2nd option
It's also worth asking what monitor you are using. No point suggesting expensive graphics if you are still stuck on a lower resolution.
As an experiment I knocked up 4 $1000 builds around a month ago. Prices are bouncing around so they aren't definitive value, but it's the 3-4 obvious options for gaming machines in that bracket.
Intel OC build - i5 3570K, HD7870XT http://pcpartpicker.com/p/AAA1
Intel non-OC build - i5 3470, GTX670 http://pcpartpicker.com/p/AAGN
AMD 6core - FX6300, GTX670 http://pcpartpicker.com/p/AAPb
AMD 8core - FX8320, HD7950 http://pcpartpicker.com/p/AAMS
I allowed $100 for a case which is fairly high, and a Caviar Black 1TB HDD which isn't cheap either. All I did was use the maximum "leftover" money on graphics, hence why the AMD 6core and i5 3470 have a $350 GTX670 because they have a fair bit more to burn. You might want to consider a small SSD in that budget range as well.
Personally, I'm inclined to stick with the two intel options for gaming. Out of the box the non-OC version will give a lot more bang for your buck, and on anything graphics limited it'll continue to be awesome. If you are up for OCing, then the 3570K is great, but it does eat into the budget a fair bit.
That makes a huge difference. To the point you can pretty much ignore the vast majority of stuff above. Unless you are planning to change your monitor soon, there's not a lot of sense spending that much money on a PC, especially if it is mainly just for Skyrim (as it's the only thing you've mentioned).
Skyrim is a bit of a CPU hog but only uses two threads so any good dual core (Pentium/i3) is almost as good as an i5. If you are stuck at 720P, then any mid range card like a HD7850 will be more than sufficient. Mods will definitely have an impact, but not enough to cause problems.
I will also be doing some recording, video editing, and I (might) be starting a YouTube channel (not sure though) running fraps, skyrim, rendering video, and maybe hosting a server? I'm gonna need a pretty good computer!